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SQL INSERT Statement

• INSERT INTO Statement: Used to add new rows to a table.

  • Syntax: INSERT INTO table_name (column1, column2,...) VALUES (value1, value2,...);

  • Optional Keyword: INTO is optional in the syntax.

  • NULL Values: If a column is assigned a NULL value:

    • If the column has a NOT NULL constraint, the insert is rejected.

  • Default Value: A default value can be specified for columns.

    • Syntax: DEFAULT value follows the keyword before the column in a CREATE TABLE statement.

  • Column Assignment: When a row is added, columns without specified values get either a NULL or default value.

SQL UPDATE Statement

• UPDATE Statement: Used to modify existing records in a table.

  • SET Clause: Specifies the new values for the columns being updated.

    • Example: UPDATE table_name SET column1 = value1, column2 = value2;

  • WHERE Clause: Optional, defines which rows are updated.

    • Omitting the WHERE clause updates all rows in the table.

SQL DELETE Statement

• DELETE Statement: Used to remove rows from a table.

  • DELETE Syntax: DELETE FROM table_name WHERE condition;

  • FROM Clause: Indicates the table from which rows will be deleted.

SQL TRUNCATE Statement

• TRUNCATE Statement: Quickly removes all rows from a table.

  • Syntax: TRUNCATE TABLE table_name;

  • Differences from DELETE:

    • Unlike DELETE, does not require a WHERE clause.

    • Typically performed faster than DELETE, as it does not log individual row deletions in most database systems.