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joplin notion extension/Web Development/sql/sqlite.md

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+sqlite
+
+- get list of databases : `.database` or `.databases`
+- get list of tables : `.tables`
+- get schemas : `.schema` , for particular table : `schema <TABLE_NAME>`
+- to show field name when using select query, make sure to switch headers on by `.headers on`
+
+
+ddl commands
+
+**alter tables**
+- `ALTER TABLE old_table_name RENAME TO new_table_name;`
+-  `ALTER TABLE table_name RENAME COLUMN old_column_name TO new_column_name;`
+-  `ALTER TABLE table_name ADD COLUMN column_name datatype;`
+-  `ALTER TABLE table_name DROP COLUMN column_name;`
+- `ALTER TABLE songdata add COLUMN is_bookmarked INTEGER DEFAULT 0`
+- `ALTER TABLE Employees ALTER COLUMN Status SET DEFAULT 'Active'` (requires new version)
+- `ALTER TABLE ... ALTER COLUMN ... DROP NOT NULL` (requires new version)
+**create tables**
+- foreign key constraint
+ `FOREIGN KEY (lyrics_url) REFERENCES lyricsUrl(lyrics_url)`
+&nbsp;
+
+dml ones
+
+  **timestamp**
+  https://www.sqlite.org/lang_datefunc.html
+  ```sql
+  CREATE TABLE event_log (
+    id INTEGER PRIMARY KEY,
+    event_name TEXT,
+    
+    -- Option A: Stores as human-readable TEXT (UTC time)
+    created_at TEXT DEFAULT CURRENT_TIMESTAMP,
+    
+    -- Option B: Stores as a Unix INTEGER timestamp (Seconds since 1970)
+    unix_timestamp INTEGER DEFAULT (strftime('%s', 'now'))
+);
+  ```
+
+```sql
+insert into event_log (id,event_name, unix_timestamp)
+values(1,'event1',unixepoch());
+```
+
+&nbsp;
+
+upsert
+```sql
+INSERT INTO table_name (column1, column2)
+VALUES (value1, value2)
+ON CONFLICT (conflict_column)
+DO UPDATE SET column1 = excluded.column1, column2 = excluded.column2;   
+```
+
+&nbsp;
+
+auto increment
+only possible for integer columns declared as primary key
+```sql
+id INTEGER PRIMARY KEY AUTOINCREMENT
+```