DELETE

    Description

    deletes rows that satisfy the WHERE clause from the specified table. If the WHERE clause is absent, the effect is to delete all rows in the table. The result is a valid, but empty table.

    By default, DELETE will delete rows in the specified table and all its child tables. If you wish to delete only from the specific table mentioned, you must use the ONLY clause.

    There are two ways to delete rows in a table using information contained in other tables in the database: using sub-selects, or specifying additional tables in the USING clause. Which technique is more appropriate depends on the specific circumstances.

    If the WHERE CURRENT OF clause is specified, the row that is deleted is the one most recently fetched from the specified cursor.

    You must have the DELETE privilege on the table to delete from it.

    Outputs

    On successful completion, a DELETE command returns a command tag of the form

      The count is the number of rows deleted. If count is 0, no rows matched the condition (this is not considered an error).

      ONLY

      If specified, delete rows from the named table only. When not specified, any tables inheriting from the named table are also processed.

      The name (optionally schema-qualified) of an existing table.

      alias

      A substitute name for the target table. When an alias is provided, it completely hides the actual name of the table. For example, given DELETE FROM foo AS f, the remainder of the DELETE statement must refer to this table as not foo.

      usinglist

      A list of table expressions, allowing columns from other tables to appear in the WHERE condition. This is similar to the list of tables that can be specified in the FROM Clause of a statement; for example, an alias for the table name can be specified. Do not repeat the target table in the usinglist, unless you wish to set up a self-join.

      condition

      An expression returning a value of type boolean, which determines the rows that are to be deleted.

      cursor_name

      The name of the cursor to use in a WHERE CURRENT OF condition. The row to be deleted is the one most recently fetched from this cursor. The cursor must be a simple (non-join, non-aggregate) query on the DELETE target table.

      WHERE CURRENT OF cannot be specified together with a Boolean condition.

      See DECLARE for more information about creating cursors.

      Notes

      Greenplum Database lets you reference columns of other tables in the WHERE condition by specifying the other tables in the USING clause. For example, to the name from the rank table, one might do:

      What is essentially happening here is a join between rank and names, with all successfully joined rows being marked for deletion. This syntax is not standard. However, this join style is usually easier to write and faster to execute than a more standard sub-select style, such as:

      1. DELETE FROM rank WHERE id IN (SELECT id FROM names WHERE name 
      2. = 'Hannah');

      Execution of UPDATE and DELETE commands directly on a specific partition (child table) of a partitioned table is not supported. Instead, these commands must be executed on the root partitioned table, the table created with the CREATE TABLE command.

      For a partitioned table, all the child tables are locked during the DELETE operation.

      Delete all films but musicals:

      Clear the table films:

      1. DELETE FROM films;

      Delete using a join:

      Compatibility

      This command conforms to the SQL standard, except that the USING clause is a Greenplum Database extension.

      , TRUNCATE