feat: add query editor above result rows

src/app.rs

@@ -1,4 +1,4 @@
-use crossterm::event::{KeyCode, KeyEvent};
+use crossterm::event::{KeyCode, KeyEvent, KeyModifiers};
 use ratatui::{
     Frame,
     layout::{Constraint, Layout, Rect},
@@ -9,10 +9,18 @@ use ratatui::{
 
 use crate::{
     Result,
-    db::{Column, Database, PAGE_SIZE, Page, Relation},
+    connection::Input,
+    db::{Column, Database, PAGE_SIZE, Page, QueryResult, Relation},
     error_text,
 };
 
+#[derive(Clone, Copy, PartialEq, Eq)]
+pub(crate) enum Focus {
+    Explorer,
+    Query,
+    Rows,
+}
+
 pub struct App {
     db: Database,
     pub(crate) relations: Vec<Relation>,
@@ -24,6 +32,8 @@ pub struct App {
     schema_state: TableState,
     column_offset: usize,
     show_schema: bool,
+    query: Input,
+    query_result: Option<QueryResult>,
     error: Option<String>,
 }
 
@@ -45,6 +55,8 @@ impl App {
             schema_state: TableState::default(),
             column_offset: 0,
             show_schema: false,
+            query: Input::default(),
+            query_result: None,
             error: None,
         };
         app.open_relation(selected);
@@ -57,7 +69,7 @@ impl App {
             KeyCode::Up | KeyCode::Char('k') => self.move_selection(-1),
             KeyCode::Home | KeyCode::Char('g') => self.move_selection(isize::MIN),
             KeyCode::End | KeyCode::Char('G') => self.move_selection(isize::MAX),
-            KeyCode::Char('s') => {
+            KeyCode::Char('s') if self.query_result.is_none() => {
                 self.show_schema = !self.show_schema;
                 self.column_offset = 0;
             }
@@ -68,16 +80,22 @@ impl App {
                 let count = if self.show_schema {
                     5
                 } else {
-                    self.columns.len()
+                    self.query_result
+                        .as_ref()
+                        .map_or(self.columns.len(), |result| result.headers.len())
                 };
                 if self.column_offset + 1 < count {
                     self.column_offset += 1;
                 }
             }
-            KeyCode::Char('n') | KeyCode::PageDown if !self.show_schema && self.page.has_next => {
+            KeyCode::Char('n') | KeyCode::PageDown
+                if self.query_result.is_none() && !self.show_schema && self.page.has_next =>
+            {
                 self.load_page(self.page_index + 1);
             }
-            KeyCode::Char('p') | KeyCode::PageUp if !self.show_schema && self.page_index > 0 => {
+            KeyCode::Char('p') | KeyCode::PageUp
+                if self.query_result.is_none() && !self.show_schema && self.page_index > 0 =>
+            {
                 self.load_page(self.page_index - 1);
             }
             KeyCode::Char('r') => self.refresh(),
@@ -85,18 +103,50 @@ impl App {
         }
     }
 
+    pub(crate) fn handle_query_key(&mut self, key: KeyEvent) {
+        match key.code {
+            KeyCode::F(5) => self.execute_query(),
+            KeyCode::Enter if key.modifiers.contains(KeyModifiers::CONTROL) => self.execute_query(),
+            KeyCode::Enter => self.query.paste_multiline("\n"),
+            _ => self.query.edit(key),
+        }
+    }
+
+    pub(crate) fn paste_query(&mut self, text: &str) {
+        self.query.paste_multiline(text);
+    }
+
+    fn execute_query(&mut self) {
+        match self.db.query(&self.query.value) {
+            Ok(result) => {
+                self.rows_state = TableState::default()
+                    .with_selected((!result.page.rows.is_empty()).then_some(0));
+                self.column_offset = 0;
+                self.show_schema = false;
+                self.query_result = Some(result);
+                self.error = None;
+            }
+            Err(error) => self.error = Some(error_text(error.as_ref())),
+        }
+    }
+
     fn move_selection(&mut self, delta: isize) {
         if self.show_schema {
             let next = moved_index(self.schema_state.selected(), self.columns.len(), delta);
             self.schema_state.select(next);
         } else {
-            let next = moved_index(self.rows_state.selected(), self.page.rows.len(), delta);
+            let count = self
+                .query_result
+                .as_ref()
+                .map_or(self.page.rows.len(), |result| result.page.rows.len());
+            let next = moved_index(self.rows_state.selected(), count, delta);
             self.rows_state.select(next);
         }
     }
 
     pub(crate) fn open_relation(&mut self, index: Option<usize>) {
         self.active = index;
+        self.query_result = None;
         self.columns.clear();
         self.page = Page {
             rows: Vec::new(),
@@ -151,10 +201,10 @@ impl App {
         }
     }
 
-    pub(crate) fn draw(&mut self, frame: &mut Frame, area: Rect, focused: bool) {
+    pub(crate) fn draw(&mut self, frame: &mut Frame, area: Rect, focus: Focus) {
         if area.width < 38 || area.height < 10 {
             frame.render_widget(
-                Paragraph::new("Enlarge terminal to at least 70×12. q to quit."),
+                Paragraph::new("Enlarge terminal to at least 70×14. Ctrl-C to quit."),
                 area,
             );
             return;
@@ -174,8 +224,18 @@ impl App {
             .style(Style::default().fg(Color::Cyan)),
             header,
         );
-        let content = body;
-        let title = if self.show_schema {
+        let [query, content] =
+            Layout::vertical([Constraint::Ratio(1, 2), Constraint::Min(4)]).areas(body);
+        self.query.draw(
+            frame,
+            query,
+            " Query · F5 execute ",
+            false,
+            focus == Focus::Query,
+        );
+        let title = if self.query_result.is_some() {
+            " Results "
+        } else if self.show_schema {
             " Schema · s for rows "
         } else {
             " Rows · s for schema "
@@ -183,7 +243,9 @@ impl App {
         let count = if self.show_schema {
             5
         } else {
-            self.columns.len()
+            self.query_result
+                .as_ref()
+                .map_or(self.columns.len(), |result| result.headers.len())
         };
         let visible = usize::from(content.width.saturating_sub(4) / 21)
             .max(1)
@@ -195,7 +257,20 @@ impl App {
                 Constraint::Length(20)
             }
         });
-        let description = if let Some(index) = self.active {
+        let description = if let Some(result) = &self.query_result {
+            format!(
+                " Query · {} rows{} · columns {}–{}/{}",
+                result.page.rows.len(),
+                if result.page.has_next {
+                    " (first 100)"
+                } else {
+                    ""
+                },
+                if count > 0 { self.column_offset + 1 } else { 0 },
+                self.column_offset + visible,
+                count,
+            )
+        } else if let Some(index) = self.active {
             let relation = &self.relations[index];
             if self.show_schema {
                 format!(
@@ -228,8 +303,12 @@ impl App {
             " No readable relations. r to refresh.".into()
         };
         let content_block =
-            panel(title, focused).title_bottom(Line::from(description).left_aligned());
-        if self.active.is_none() {
+            panel(title, focus == Focus::Rows).title_bottom(Line::from(description).left_aligned());
+        let page = self
+            .query_result
+            .as_ref()
+            .map_or(&self.page, |result| &result.page);
+        if self.active.is_none() && self.query_result.is_none() {
             frame.render_widget(
                 Paragraph::new("Choose a relation and press Enter.").block(content_block),
                 content,
@@ -259,7 +338,7 @@ impl App {
                 .row_highlight_style(selected_style())
                 .highlight_symbol("› ");
             frame.render_stateful_widget(table, content, &mut self.schema_state);
-        } else if self.page.rows.is_empty() {
+        } else if page.rows.is_empty() {
             frame.render_widget(
                 Paragraph::new(if self.error.is_some() {
                     "Could not load rows. See error above."
@@ -270,13 +349,13 @@ impl App {
                 content,
             );
         } else {
-            let headers = self
-                .columns
-                .iter()
-                .skip(self.column_offset)
-                .take(visible)
-                .map(|column| column.label.as_str());
-            let rows = self.page.rows.iter().map(|row| {
+            let headers = (self.column_offset..self.column_offset + visible).map(|index| {
+                self.query_result.as_ref().map_or_else(
+                    || self.columns[index].label.as_str(),
+                    |result| result.headers[index].as_str(),
+                )
+            });
+            let rows = page.rows.iter().map(|row| {
                 Row::new(
                     row.iter()
                         .skip(self.column_offset)
@@ -353,6 +432,37 @@ mod tests {
         assert_eq!(moved_index(Some(1), 3, isize::MAX), Some(2));
     }
 
+    #[test]
+    fn queries_replace_rows_and_preserve_results_on_error() -> crate::Result<()> {
+        use crossterm::event::{KeyCode, KeyEvent, KeyModifiers};
+        let file = tempfile::NamedTempFile::new()?;
+        rusqlite::Connection::open(file.path())?.execute_batch(
+            "CREATE TABLE comments (id INTEGER); INSERT INTO comments VALUES (9);",
+        )?;
+        let mut app = super::App::new(crate::db::Database::open_sqlite(file.path())?)?;
+        app.paste_query("SELECT '界é' AS note,\nNULL AS missing UNION ALL SELECT 'next', 2;");
+        app.handle_query_key(KeyEvent::new(KeyCode::F(5), KeyModifiers::NONE));
+        let result = app.query_result.as_ref().unwrap();
+        assert_eq!(result.headers, ["note", "missing"]);
+        assert_eq!(result.page.rows[0], [Some("界é".into()), None]);
+        app.handle_key(KeyEvent::new(KeyCode::Down, KeyModifiers::NONE));
+        assert_eq!(app.rows_state.selected(), Some(1));
+        app.handle_query_key(KeyEvent::new(KeyCode::Char('u'), KeyModifiers::CONTROL));
+        app.paste_query("SELECT missing FROM nowhere");
+        app.handle_query_key(KeyEvent::new(KeyCode::Enter, KeyModifiers::CONTROL));
+        assert!(app.error.is_some());
+        assert_eq!(
+            app.query_result.as_ref().unwrap().page.rows[0][0].as_deref(),
+            Some("界é")
+        );
+        app.open_relation(Some(0));
+        assert!(app.query_result.is_none());
+        assert!(app.error.is_none());
+        assert_eq!(app.page.rows, [vec![Some("9".into())]]);
+        assert_eq!(app.query.value, "SELECT missing FROM nowhere");
+        Ok(())
+    }
+
     #[test]
     fn relation_status_is_in_the_bottom_border() -> crate::Result<()> {
         let file = tempfile::NamedTempFile::new()?;
@@ -364,7 +474,7 @@ mod tests {
         for (schema, error) in [(false, None), (true, None), (false, Some("Read failed"))] {
             app.show_schema = schema;
             app.error = error.map(str::to_owned);
-            terminal.draw(|frame| app.draw(frame, frame.area(), true))?;
+            terminal.draw(|frame| app.draw(frame, frame.area(), super::Focus::Rows))?;
             let buffer = terminal.backend().buffer();
             let border: String = (0..100).map(|x| buffer[(x, 19)].symbol()).collect();
             assert!(border.starts_with("└ main.comments [table]"), "{border}");

src/connection.rs

@@ -13,14 +13,19 @@ use ratatui::{
     widgets::{Block, Clear, List, ListItem, ListState, Paragraph, Wrap},
 };
 
-use crate::{Result, app::App, db::Database, error_text};
+use crate::{
+    Result,
+    app::{App, Focus},
+    db::Database,
+    error_text,
+};
 
 pub fn run(terminal: &mut DefaultTerminal, initial: Option<Database>) -> Result<()> {
     let mut profiles = Profiles::open(&config_path()?)?;
     let mut browser = initial.map(App::new).transpose()?;
     let mut selection =
         ListState::default().with_selected((!profiles.entries.is_empty()).then_some(0));
-    let mut databases_focus = true;
+    let mut focus = Focus::Explorer;
     let mut active = None;
     let mut expanded = true;
     let mut error: Option<String> = None;
@@ -34,9 +39,11 @@ pub fn run(terminal: &mut DefaultTerminal, initial: Option<Database>) -> Result<
             expanded,
         );
         terminal.draw(|frame| {
-            let navigation = Paragraph::new(
-                " Tab focus · Esc explorer · ↑↓/jk move · Enter open · s schema/rows · ←→/hl columns · n/p page · r refresh · c add database · q quit"
-            ).wrap(Wrap { trim: true }).style(Style::default().fg(Color::DarkGray));
+            let navigation = Paragraph::new(if focus == Focus::Query && !show_form {
+                " Tab/Shift-Tab focus · Esc explorer · Enter newline · F5/Ctrl-Enter execute · Ctrl-U clear · Ctrl-C quit"
+            } else {
+                " Tab/Shift-Tab focus · Esc explorer · ↑↓/jk move · Enter open · s schema/rows · ←→/hl columns · n/p page · r refresh · c add database · q quit"
+            }).wrap(Wrap { trim: true }).style(Style::default().fg(Color::DarkGray));
             let help_height = navigation.line_count(frame.area().width) as u16;
             let [main, help] =
                 Layout::vertical([Constraint::Min(1), Constraint::Length(help_height)]).areas(frame.area());
@@ -57,11 +64,11 @@ pub fn run(terminal: &mut DefaultTerminal, initial: Option<Database>) -> Result<
             });
             let list = List::new(items)
                 .block(Block::bordered().title(" Explorer · c add ").border_style(
-                    Style::default().fg(if databases_focus { Color::Cyan } else { Color::DarkGray })))
+                    Style::default().fg(if focus == Focus::Explorer { Color::Cyan } else { Color::DarkGray })))
                 .highlight_style(Style::default().bg(Color::Blue).fg(Color::White));
             frame.render_stateful_widget(list, sidebar, &mut selection);
             if let Some(browser) = &mut browser {
-                browser.draw(frame, content, !databases_focus);
+                browser.draw(frame, content, focus);
             } else {
                 frame.render_widget(Paragraph::new("Select a database and press Enter to connect.\n\nc: add a database · Tab: focus · q: quit").block(Block::bordered().title(" dbdash · READ ONLY ")), content);
             }
@@ -97,7 +104,7 @@ pub fn run(terminal: &mut DefaultTerminal, initial: Option<Database>) -> Result<
                                     });
                                     selection.select(active);
                                     expanded = true;
-                                    databases_focus = true;
+                                    focus = Focus::Explorer;
                                 })
                             } else {
                                 profiles.save(&form).map(|()| {
@@ -113,7 +120,7 @@ pub fn run(terminal: &mut DefaultTerminal, initial: Option<Database>) -> Result<
                                                 profiles.entries.len() - 1,
                                             ))
                                     }));
-                                    databases_focus = true;
+                                    focus = Focus::Explorer;
                                 })
                             };
                             match result {
@@ -129,25 +136,32 @@ pub fn run(terminal: &mut DefaultTerminal, initial: Option<Database>) -> Result<
                     }
                 } else {
                     match key.code {
+                        KeyCode::Esc => focus = Focus::Explorer,
+                        KeyCode::Tab | KeyCode::BackTab if browser.is_some() => {
+                            focus = match (focus, key.code == KeyCode::BackTab) {
+                                (Focus::Explorer, false) | (Focus::Rows, true) => Focus::Query,
+                                (Focus::Query, false) | (Focus::Explorer, true) => Focus::Rows,
+                                _ => Focus::Explorer,
+                            };
+                        }
+                        _ if focus == Focus::Query => {
+                            if let Some(browser) = &mut browser {
+                                browser.handle_query_key(key);
+                            }
+                        }
                         KeyCode::Char('q') => return Ok(()),
                         KeyCode::Char('c') => {
                             form = Form::default();
                             show_form = true;
                         }
-                        KeyCode::Esc => databases_focus = true,
-                        KeyCode::Tab | KeyCode::BackTab => {
-                            if browser.is_some() {
-                                databases_focus = !databases_focus;
-                            }
-                        }
-                        KeyCode::Enter if databases_focus => {
+                        KeyCode::Enter if focus == Focus::Explorer => {
                             if let Some(entry) =
                                 selection.selected().and_then(|index| entries.get(index))
                             {
                                 let index = match *entry {
                                     ExplorerEntry::Relation(index) => {
                                         browser.as_mut().unwrap().open_relation(Some(index));
-                                        databases_focus = false;
+                                        focus = Focus::Rows;
                                         continue;
                                     }
                                     ExplorerEntry::Database(index)
@@ -171,7 +185,7 @@ pub fn run(terminal: &mut DefaultTerminal, initial: Option<Database>) -> Result<
                                             active = Some(index);
                                             selection.select(Some(index));
                                             expanded = true;
-                                            databases_focus = true;
+                                            focus = Focus::Explorer;
                                             error = None;
                                         }
                                         Err(failure) => error = Some(error_text(failure.as_ref())),
@@ -179,7 +193,7 @@ pub fn run(terminal: &mut DefaultTerminal, initial: Option<Database>) -> Result<
                                 }
                             }
                         }
-                        KeyCode::Left | KeyCode::Char('h') if databases_focus => {
+                        KeyCode::Left | KeyCode::Char('h') if focus == Focus::Explorer => {
                             if matches!(
                                 selection.selected().and_then(|index| entries.get(index)),
                                 Some(ExplorerEntry::Relation(_))
@@ -194,31 +208,31 @@ pub fn run(terminal: &mut DefaultTerminal, initial: Option<Database>) -> Result<
                                 );
                             }
                         }
-                        KeyCode::Right | KeyCode::Char('l') if databases_focus => {
+                        KeyCode::Right | KeyCode::Char('l') if focus == Focus::Explorer => {
                             if selection.selected().and_then(|index| entries.get(index))
                                 == Some(&ExplorerEntry::Database(active))
                             {
                                 expanded = true;
                             }
                         }
-                        KeyCode::Char('r') if databases_focus => {
+                        KeyCode::Char('r') if focus == Focus::Explorer => {
                             if let Some(browser) = &mut browser {
                                 browser.handle_key(key);
                             }
                         }
-                        KeyCode::Down | KeyCode::Char('j') if databases_focus => {
+                        KeyCode::Down | KeyCode::Char('j') if focus == Focus::Explorer => {
                             selection.select_next()
                         }
-                        KeyCode::Up | KeyCode::Char('k') if databases_focus => {
+                        KeyCode::Up | KeyCode::Char('k') if focus == Focus::Explorer => {
                             selection.select_previous()
                         }
-                        KeyCode::Home | KeyCode::Char('g') if databases_focus => {
+                        KeyCode::Home | KeyCode::Char('g') if focus == Focus::Explorer => {
                             selection.select_first()
                         }
-                        KeyCode::End | KeyCode::Char('G') if databases_focus => {
+                        KeyCode::End | KeyCode::Char('G') if focus == Focus::Explorer => {
                             selection.select_last()
                         }
-                        _ if !databases_focus => {
+                        _ if focus == Focus::Rows => {
                             if let Some(browser) = &mut browser {
                                 browser.handle_key(key);
                             }
@@ -233,6 +247,11 @@ pub fn run(terminal: &mut DefaultTerminal, initial: Option<Database>) -> Result<
                     input.paste(&text);
                 }
             }
+            Event::Paste(text) if focus == Focus::Query => {
+                if let Some(browser) = &mut browser {
+                    browser.paste_query(&text);
+                }
+            }
             _ => {}
         }
     }
@@ -617,8 +636,8 @@ impl Form {
 }
 
 #[derive(Clone, Default)]
-struct Input {
-    value: String,
+pub(crate) struct Input {
+    pub(crate) value: String,
     cursor: usize,
 }
 
@@ -632,7 +651,7 @@ impl From<&str> for Input {
 }
 
 impl Input {
-    fn edit(&mut self, key: KeyEvent) {
+    pub(crate) fn edit(&mut self, key: KeyEvent) {
         match key.code {
             KeyCode::Left => {
                 self.cursor = self.value[..self.cursor]
@@ -646,8 +665,39 @@ impl Input {
                     .next()
                     .map_or(0, char::len_utf8)
             }
-            KeyCode::Home => self.cursor = 0,
-            KeyCode::End => self.cursor = self.value.len(),
+            KeyCode::Up | KeyCode::Down => {
+                let start = self.value[..self.cursor].rfind('\n').map_or(0, |i| i + 1);
+                let column = self.value[start..self.cursor].chars().count();
+                let target = if key.code == KeyCode::Up {
+                    start
+                        .checked_sub(1)
+                        .map(|end| (self.value[..end].rfind('\n').map_or(0, |i| i + 1), end))
+                } else {
+                    self.value[self.cursor..].find('\n').map(|i| {
+                        let start = self.cursor + i + 1;
+                        let end = self.value[start..]
+                            .find('\n')
+                            .map_or(self.value.len(), |i| start + i);
+                        (start, end)
+                    })
+                };
+                if let Some((start, end)) = target {
+                    self.cursor = start
+                        + self.value[start..end]
+                            .chars()
+                            .take(column)
+                            .map(char::len_utf8)
+                            .sum::<usize>();
+                }
+            }
+            KeyCode::Home => {
+                self.cursor = self.value[..self.cursor].rfind('\n').map_or(0, |i| i + 1);
+            }
+            KeyCode::End => {
+                self.cursor += self.value[self.cursor..]
+                    .find('\n')
+                    .unwrap_or(self.value.len() - self.cursor);
+            }
             KeyCode::Backspace if self.cursor > 0 => {
                 let previous = self.value[..self.cursor]
                     .char_indices()
@@ -686,21 +736,41 @@ impl Input {
         self.cursor += text.len();
     }
 
-    fn draw(&self, frame: &mut Frame, area: Rect, label: &str, secret: bool, focused: bool) {
+    pub(crate) fn paste_multiline(&mut self, value: &str) {
+        let text: String = value
+            .chars()
+            .map(|character| if character == '\t' { ' ' } else { character })
+            .filter(|character| *character == '\n' || !character.is_control())
+            .collect();
+        self.value.insert_str(self.cursor, &text);
+        self.cursor += text.len();
+    }
+
+    pub(crate) fn draw(
+        &self,
+        frame: &mut Frame,
+        area: Rect,
+        label: &str,
+        secret: bool,
+        focused: bool,
+    ) {
         let text: Cow<'_, str> = if secret {
             Cow::Owned("•".repeat(self.value.chars().count()))
         } else {
             Cow::Borrowed(&self.value)
         };
+        let prefix = &self.value[..self.cursor];
+        let row = u16::try_from(prefix.matches('\n').count()).unwrap_or(u16::MAX);
+        let row_offset = row.saturating_sub(area.height.saturating_sub(3));
         let before_cursor = if secret {
             self.value[..self.cursor].chars().count()
         } else {
-            Line::raw(&self.value[..self.cursor]).width()
+            Line::raw(prefix.rsplit('\n').next().unwrap_or("")).width()
         };
         let cursor = u16::try_from(before_cursor).unwrap_or(u16::MAX);
         let offset = cursor.saturating_sub(area.width.saturating_sub(3));
         frame.render_widget(
-            Paragraph::new(text).scroll((0, offset)).block(
+            Paragraph::new(text).scroll((row_offset, offset)).block(
                 Block::bordered()
                     .title(label)
                     .border_style(Style::default().fg(if focused {
@@ -712,7 +782,8 @@ impl Input {
             area,
         );
         if focused && area.width > 2 && area.height > 2 {
-            frame.set_cursor_position((area.x + 1 + cursor - offset, area.y + 1));
+            frame
+                .set_cursor_position((area.x + 1 + cursor - offset, area.y + 1 + row - row_offset));
         }
     }
 }
@@ -765,6 +836,24 @@ mod tests {
         assert_eq!(input.cursor, 0);
     }
 
+    #[test]
+    fn multiline_editing_preserves_lines_and_unicode() {
+        let mut input = Input::default();
+        input.paste_multiline("aé界\nxy\nz\r\n\t\u{1b}");
+        assert_eq!(input.value, "aé界\nxy\nz\n ");
+        for code in [KeyCode::Up, KeyCode::Up, KeyCode::Up] {
+            input.edit(KeyEvent::new(code, KeyModifiers::NONE));
+        }
+        assert_eq!(&input.value[..input.cursor], "a");
+        input.edit(KeyEvent::new(KeyCode::End, KeyModifiers::NONE));
+        input.edit(KeyEvent::new(KeyCode::Down, KeyModifiers::NONE));
+        assert_eq!(&input.value[..input.cursor], "aé界\nxy");
+        input.edit(KeyEvent::new(KeyCode::Home, KeyModifiers::NONE));
+        input.edit(KeyEvent::new(KeyCode::Backspace, KeyModifiers::NONE));
+        assert_eq!(input.value, "aé界xy\nz\n ");
+        assert_eq!(input.cursor, "aé界".len());
+    }
+
     #[test]
     fn password_never_appears_in_the_connection_screen() -> Result<()> {
         let mut form = Form {

src/db.rs

@@ -46,6 +46,11 @@ pub struct Page {
     pub has_next: bool,
 }
 
+pub struct QueryResult {
+    pub headers: Vec<String>,
+    pub page: Page,
+}
+
 impl Database {
     pub fn connect(connection: &str) -> Result<Self> {
         Self::connect_postgres(connection.parse()?)
@@ -157,6 +162,59 @@ impl Database {
             .collect())
     }
 
+    pub fn query(&mut self, sql: &str) -> Result<QueryResult> {
+        let sql = sql.trim();
+        let sql = sql.strip_suffix(';').unwrap_or(sql).trim_end();
+        let client = match &mut self.backend {
+            Backend::Postgres(client) => client,
+            Backend::Sqlite(connection) => return sqlite::query(connection, sql),
+        };
+        let mut transaction = client.build_transaction().read_only(true).start()?;
+        transaction.batch_execute("SET LOCAL statement_timeout = '5s'")?;
+        let statement = transaction.prepare(&format!(
+            "SELECT * FROM (\n{sql}\n) AS query_result LIMIT 0"
+        ))?;
+        let headers = statement
+            .columns()
+            .iter()
+            .map(|column| display_text(column.name()))
+            .collect::<Vec<_>>();
+        let aliases = (0..headers.len())
+            .map(|index| format!("c{index}"))
+            .collect::<Vec<_>>();
+        let projection = aliases
+            .iter()
+            .map(|alias| format!("query_result.{alias}::text"))
+            .collect::<Vec<_>>()
+            .join(", ");
+        let alias_list = if aliases.is_empty() {
+            String::new()
+        } else {
+            format!("({})", aliases.join(", "))
+        };
+        let result = transaction.query(
+            &format!(
+                "SELECT {projection} FROM (\n{sql}\n) AS query_result{alias_list} LIMIT {}",
+                PAGE_SIZE + 1
+            ),
+            &[],
+        )?;
+        let has_next = result.len() > PAGE_SIZE;
+        let rows = result
+            .into_iter()
+            .take(PAGE_SIZE)
+            .map(|row| {
+                (0..headers.len())
+                    .map(|index| row.get::<_, Option<&str>>(index).map(display_text))
+                    .collect()
+            })
+            .collect();
+        Ok(QueryResult {
+            headers,
+            page: Page { rows, has_next },
+        })
+    }
+
     pub fn page(&mut self, relation: &Relation, columns: &[Column], page: usize) -> Result<Page> {
         let client = match &mut self.backend {
             Backend::Postgres(client) => client,
@@ -319,9 +377,55 @@ mod tests {
         let page = db.page(empty, &columns, 0)?;
         assert!(page.rows.is_empty());
         assert!(!page.has_next);
+        let query = db.query(&format!(
+            " \nWITH data AS (SELECT * FROM {schema}.\"odd\"\"table\")
+             SELECT * FROM data ORDER BY id; \n"
+        ))?;
+        assert_eq!(query.headers[1], "odd\"column");
+        assert_eq!(query.page.rows, first.rows);
+        assert!(query.page.has_next);
+        let duplicate = db.query("SELECT 1 AS same, NULL::text AS same")?;
+        assert_eq!(duplicate.headers, ["same", "same"]);
+        assert_eq!(duplicate.page.rows, [vec![Some("1".into()), None]]);
+        assert!(!duplicate.page.has_next);
+        let empty = db.query("SELECT 1 AS empty WHERE false")?;
+        assert_eq!(empty.headers, ["empty"]);
+        assert!(empty.page.rows.is_empty());
+        assert!(!empty.page.has_next);
+        let controls = db.query("SELECT E'\\033[2J' AS \"line\nheader\" -- trailing comment")?;
+        assert_eq!(controls.headers, ["line\\nheader"]);
+        assert_eq!(controls.page.rows[0][0].as_deref(), Some("\\u{1b}[2J"));
+        assert!(db.query("SELECT 1; SELECT 2").is_err());
+        assert!(
+            db.query(&format!("DELETE FROM {schema}.empty_table RETURNING id"))
+                .is_err()
+        );
+        assert!(
+            db.query(&format!(
+                "WITH deleted AS (DELETE FROM {schema}.empty_table RETURNING id)
+                 SELECT * FROM deleted"
+            ))
+            .is_err()
+        );
+        db.query("SELECT set_config('default_transaction_read_only', 'off', false)")?;
+        let settings = db.query("SELECT current_setting('default_transaction_read_only')")?;
+        assert_eq!(settings.page.rows[0][0].as_deref(), Some("on"));
+        if let Backend::Postgres(client) = &mut db.backend {
+            client.batch_execute(
+                "SET default_transaction_read_only = off; SET statement_timeout = 0",
+            )?;
+        }
+        let settings = db.query(
+            "SELECT current_setting('transaction_read_only'), current_setting('statement_timeout')",
+        )?;
+        assert_eq!(
+            settings.page.rows[0],
+            [Some("on".into()), Some("5s".into())]
+        );
         let Backend::Postgres(client) = &mut db.backend else {
             unreachable!()
         };
+        client.batch_execute("SET default_transaction_read_only = on")?;
         let error = client
             .batch_execute(&format!("DELETE FROM {schema}.empty_table"))
             .unwrap_err();

src/db/sqlite.rs

@@ -2,7 +2,9 @@ use std::{fmt::Write, path::Path, time::Duration};
 
 use rusqlite::{Connection, OpenFlags, params, types::ValueRef};
 
-use super::{Column, PAGE_SIZE, Page, Relation, display_text, page_offset, quote_identifier};
+use super::{
+    Column, PAGE_SIZE, Page, QueryResult, Relation, display_text, page_offset, quote_identifier,
+};
 use crate::Result;
 
 pub(super) fn open(path: &Path) -> Result<Connection> {
@@ -109,6 +111,26 @@ pub(super) fn page(
     );
     let mut statement = connection.prepare(&sql)?;
     let mut query = statement.query(params![(PAGE_SIZE + 1) as i64, page_offset(page)?])?;
+    read_page(&mut query, columns.len())
+}
+
+pub(super) fn query(connection: &Connection, sql: &str) -> Result<QueryResult> {
+    let original = connection.prepare(sql)?;
+    let headers = original
+        .column_names()
+        .into_iter()
+        .map(display_text)
+        .collect();
+    let mut statement = connection.prepare(&format!(
+        "SELECT * FROM (\n{sql}\n) AS query_result LIMIT {}",
+        PAGE_SIZE + 1
+    ))?;
+    let column_count = statement.column_count();
+    let page = read_page(&mut statement.query([])?, column_count)?;
+    Ok(QueryResult { headers, page })
+}
+
+fn read_page(query: &mut rusqlite::Rows<'_>, column_count: usize) -> Result<Page> {
     let mut rows = Vec::with_capacity(PAGE_SIZE);
     while let Some(row) = query.next()? {
         if rows.len() == PAGE_SIZE {
@@ -117,7 +139,7 @@ pub(super) fn page(
                 has_next: true,
             });
         }
-        let values = (0..columns.len())
+        let values = (0..column_count)
             .map(|index| {
                 Ok(match row.get_ref(index)? {
                     ValueRef::Null => None,
@@ -154,6 +176,68 @@ mod tests {
     use super::*;
     use crate::db::{Backend, Database};
 
+    #[test]
+    fn query_sqlite_read_only() -> Result<()> {
+        let directory = tempfile::tempdir()?;
+        let path = directory.path().join("queries.sqlite");
+        let writer = Connection::open(&path)?;
+        writer
+            .execute_batch("CREATE TABLE saved (value INTEGER); INSERT INTO saved VALUES (7);")?;
+        let mut db = Database::open_sqlite(&path)?;
+
+        let result = db.query(
+            " \nSELECT NULL AS \"same\", X'00FF' AS \"same\", char(27) || '[2J' AS \"line
+break\", 2.5 AS amount; \n",
+        )?;
+        assert_eq!(result.headers, ["same", "same", "line\\nbreak", "amount"]);
+        assert_eq!(
+            result.page.rows,
+            vec![vec![
+                None,
+                Some("X'00FF'".into()),
+                Some("\\u{1b}[2J".into()),
+                Some("2.5".into())
+            ]]
+        );
+        assert!(!result.page.has_next);
+        let empty = db.query("SELECT value AS original FROM saved WHERE 0")?;
+        assert_eq!(empty.headers, ["original"]);
+        assert!(empty.page.rows.is_empty());
+        assert!(!empty.page.has_next);
+
+        let result = db.query(
+            "WITH RECURSIVE numbers(n) AS (
+                SELECT 1 UNION ALL SELECT n + 1 FROM numbers WHERE n < 101
+             ) SELECT n FROM numbers -- trailing comment",
+        )?;
+        assert_eq!(result.headers, ["n"]);
+        assert_eq!(result.page.rows.len(), PAGE_SIZE);
+        assert_eq!(result.page.rows[99][0].as_deref(), Some("100"));
+        assert!(result.page.has_next);
+        let exact = db.query(
+            "WITH RECURSIVE numbers(n) AS (
+                SELECT 1 UNION ALL SELECT n + 1 FROM numbers WHERE n < 100
+             ) SELECT n FROM numbers",
+        )?;
+        assert_eq!(exact.page.rows.len(), PAGE_SIZE);
+        assert!(!exact.page.has_next);
+
+        for sql in [
+            "DELETE FROM saved",
+            "UPDATE saved SET value = 8 RETURNING value",
+            "DROP TABLE saved",
+            "SELECT value FROM saved; DELETE FROM saved",
+            "PRAGMA query_only = OFF",
+        ] {
+            assert!(db.query(sql).is_err(), "accepted write: {sql}");
+            assert_eq!(
+                db.query("SELECT value FROM saved")?.page.rows,
+                vec![vec![Some("7".into())]]
+            );
+        }
+        Ok(())
+    }
+
     #[test]
     fn inspect_sqlite_read_only() -> Result<()> {
         let directory = tempfile::tempdir()?;

src/main.rs

@@ -26,23 +26,30 @@ Expansion never runs shell commands. Quote CLI paths to let dbdash expand them.
 PostgreSQL URLs and libpq-style key=value strings are accepted.
 Use sslmode=require for mandatory TLS; certificates and hostnames are verified.
 Use sslmode=disable only for trusted local connections.
-The inspector needs 70×12 terminal cells; the PostgreSQL window needs 74×20.
+The inspector needs 70×14 terminal cells; the PostgreSQL window needs 74×20.
 
 Navigation:
-  Tab/Shift-Tab Switch between explorer and rows/schema (Esc returns to explorer)
+  Tab/Shift-Tab Cycle explorer, query editor, and rows/schema (Esc returns to explorer)
   Up/Down, j/k  Move selection; Enter connects/expands a database or opens a relation
   Home/End, g/G First / last item
   s             Toggle rows and column schema
   Left/Right    Collapse/expand in explorer; scroll columns in rows/schema (h/l too)
-  n/p, PgDn/Up  Next / previous 100-row page
+  n/p, PgDn/Up  Next / previous 100-row relation page
   c             Add a configured database in a floating window
   r             Refresh relations and the active relation
   Connected databases show their tables and views beneath them in the explorer.
   Enter on the connected database collapses/expands it without reconnecting.
   Navigation help spans the bottom as one line, wrapping only when needed.
+  The query editor sits above rows/results; the explorer spans both panes.
   Explorer and rows/schema bottom borders align; relation/page/column status
-  appears in the rows/schema border. Read errors appear above that pane.
-  q / Ctrl-C    Quit
+  appears in the rows/schema border. Read errors appear above the query editor.
+  In the query editor, type SQL directly; Enter inserts a newline. Arrow keys,
+  Home/End, Backspace/Delete, Ctrl-U (clear), and multiline pasting are supported.
+  F5 / Ctrl-Enter executes one SELECT/CTE on the current connection, showing up
+  to 100 rows below. Results report truncation; use SQL LIMIT/OFFSET for more.
+  Failed queries keep the previous results. Opening a relation restores browsing
+  without clearing the query text. Query text is not saved across connections.
+  q / Ctrl-C    Quit (q is literal text in the query editor)
   New database window: Up/Down chooses a provider; Enter starts editing.
   Tab/Shift-Tab changes fields; Left/Right changes TLS when that field is focused.
   Enter saves without connecting, including when the database is offline.