Tag: mysql

12.2.5.1. INSERT ... SELECT Syntax

INSERT [LOW_PRIORITY | HIGH_PRIORITY] [IGNORE]    [INTO] tbl_name [(col_name,...)]    SELECT ...    [ ON DUPLICATE KEY UPDATE col_name=expr, ... ]

With INSERT ... SELECT, you can quickly insert many rows into a table from one or many tables. For example:

INSERT INTO tbl_temp2 (fld_id)  SELECT tbl_temp1.fld_order_id  FROM tbl_temp1 WHERE tbl_temp1.fld_order_id > 100;

The following conditions hold for a INSERT ... SELECT statements:

• Specify IGNORE to ignore rows that would cause duplicate-key violations.

• DELAYED is ignored with INSERT ... SELECT.

• The target table of the INSERT statement may appear in the FROM clause of the SELECT part of the query. (This was not possible in some older versions of MySQL.) However, you cannot insert into a table and select from the same table in a subquery.

  When selecting from and inserting into a table at the same time, MySQL creates a temporary table to hold the rows from the SELECT and then inserts those rows into the target table. However, it remains true that you cannot use INSERT INTO t ... SELECT ... FROM t when t is a TEMPORARY table, because TEMPORARY tables cannot be referred to twice in the same statement (see Section C.5.7.2, “TEMPORARY Table Problems”).

• AUTO_INCREMENT columns work as usual.

• To ensure that the binary log can be used to re-create the original tables, MySQL does not permit concurrent inserts for INSERT ... SELECT statements.

• To avoid ambiguous column reference problems when the SELECT and the INSERT refer to the same table, provide a unique alias for each table used in the SELECT part, and qualify column names in that part with the appropriate alias.

In the values part of ON DUPLICATE KEY UPDATE, you can refer to columns in other tables, as long as you do not use GROUP BY in the SELECT part. One side effect is that you must qualify nonunique column names in the values part.

The order in which rows are returned by a SELECT statement with no ORDER BY clause is not determined. This means that, when using replication, there is no guarantee that such a SELECT returns rows in the same order on the master and the slave; this can lead to inconsistencies between them. To prevent this from occurring, you should always write INSERT ... SELECT statements that are to be replicated as INSERT ... SELECT ... ORDER BY column. The choice of column does not matter as long as the same order for returning the rows is enforced on both the master and the slave. See also Section 15.4.1.9, “Replication and LIMIT”.