SELECT INTO

Function

SELECT INTO defines a new table based on a query result and inserts data obtained by query to the new table.

Different from SELECT, data found by SELECT INTO is not returned to the client. The table columns have the same names and data types as the output columns of the SELECT.

Precautions

CREATE TABLE AS provides functions similar to SELECT INTO in functions and provides a superset of functions provided by SELECT INTO. You are advised to use CREATE TABLE AS, because SELECT INTO cannot be used in a stored procedure.

Syntax

SelectInto ::= [ WITH [ RECURSIVE ] with_query [, ...] ]
SELECT [ ALL | DISTINCT [ ON ( expression [, ...] ) ] ]
    { * | {expression [ [ AS ] output_name ]} [, ...] }
    INTO [ [ GLOBAL | LOCAL ] [ TEMPORARY | TEMP ] | UNLOGGED ] [ TABLE ] new_table
    [ FROM from_item [, ...] ]
    [ WHERE condition ]
    [ GROUP BY expression [, ...] ]
    [ HAVING condition [, ...] ]
    [ WINDOW {window_name AS ( window_definition )} [, ...] ]
    [ { UNION | INTERSECT | EXCEPT | MINUS } [ ALL | DISTINCT ] select ]
    [ ORDER BY {expression [ [ ASC | DESC | USING operator ] | nlssort_expression_clause ] [ NULLS { FIRST | LAST } ]} [, ...] ]
    [ LIMIT { count | ALL } ]
    [ OFFSET start [ ROW | ROWS ] ]
    [ FETCH { FIRST | NEXT } [ count ] { ROW | ROWS } ONLY ]
    [ {FOR { UPDATE | SHARE } [ OF table_name [, ...] ] [ NOWAIT ]} [...] ];

Parameter Description

• new_table

  new_table specifies the name of the new table.

• UNLOGGED

  Specifies that the table is created as an unlogged table. Data written to unlogged tables is not written to the WALs, which makes them considerably faster than ordinary tables. However, they are not crash-safe: an unlogged table is automatically truncated after a crash or unclean shutdown. The contents of an unlogged table are also not replicated to standby servers. Any indexes created on an unlogged table are automatically unlogged as well.

  • Usage scenario: Unlogged tables do not ensure data security. Users can back up data before using unlogged tables; for example, users should back up the data before a system upgrade.
  • Troubleshooting: If data is missing in the indexes of unlogged tables due to some unexpected operations such as an unclean shutdown, users should re-create the indexes with errors.

• GLOBAL | LOCAL

  When creating a temporary table, you can specify the GLOBAL or LOCAL keyword before TEMP or TEMPORARY. If the keyword GLOBAL is specified, MogDB creates a global temporary table. Otherwise, MogDB creates a local temporary table.

• TEMPORARY | TEMP

  If TEMP or TEMPORARY is specified, the created table is a temporary table. Temporary tables are classified into global temporary tables and local temporary tables. If the keyword GLOBAL is specified when a temporary table is created, the table is a global temporary table. Otherwise, the table is a local temporary table.

  The metadata of the global temporary table is visible to all sessions. After the sessions end, the metadata still exists. The user data, indexes, and statistics of a session are isolated from those of another session. Each session can only view and modify the data submitted by itself. Global temporary tables have two schemas: ON COMMIT PRESERVE ROWS and ON COMMIT PRESERVE ROWS. In session-based ON COMMIT PRESERVE ROWS schema, user data is automatically cleared when a session ends. In transaction-based ON COMMIT DELETE ROWS schema, user data is automatically cleared when the commit or rollback operation is performed. If the ON COMMIT option is not specified during table creation, the session level is used by default. Different from local temporary tables, you can specify a schema that does not start with pg_temp_ when creating a global temporary table.

  A local temporary table is automatically dropped at the end of the current session. Therefore, you can create and use temporary tables in the current session as long as the connected database node in the session is normal. Temporary tables are created only in the current session. If a DDL statement involves operations on temporary tables, a DDL error will be generated. Therefore, you are not advised to perform operations on temporary tables in DDL statements. TEMP is equivalent to TEMPORARY.

  NOTICE:

  • Local temporary tables are visible to the current session through the schema starting with pg_temp start. Users should not delete schema started with pg_temp or pg_toast_temp.
  • If TEMPORARY or TEMP is not specified when you create a table but its schema is set to that starting with pg_temp_ in the current session, the table will be created as a temporary table.
  • If global temporary tables and indexes are being used by other sessions, do not perform ALTER or DROP.
  • The DDL of a global temporary table affects only the user data and indexes of the current session. For example, TRUNCATE, REINDEX, and ANALYZE are valid only for the current session.

NOTE: For details about other SELECT INTO parameters, see Parameter Description in SELECT.

Examples

-- Add the values that are less than 5 in the r_reason_sk field in the tpcds.reason table to the new table.
MogDB=# SELECT * INTO tpcds.reason_t1 FROM tpcds.reason WHERE r_reason_sk < 5;
INSERT 0 6

-- Delete the  tpcds.reason_t1 table.
MogDB=# DROP TABLE tpcds.reason_t1;

Helpful Links

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