27.7.6.38 mysql_insert_id()
my_ulonglong mysql_insert_id(MYSQL *mysql)
Returns the value generated for an AUTO_INCREMENT
column by the previous INSERT
or UPDATE
statement. Use this function after you have performed an INSERT
statement into a table that contains an AUTO_INCREMENT
field, or have used INSERT
or UPDATE
to set a column value with LAST_INSERT_ID(
. expr
)
The return value of mysql_insert_id()
is always zero unless explicitly updated under one of the following conditions:
INSERT
statements that store a value into anAUTO_INCREMENT
column. This is true whether the value is automatically generated by storing the special valuesNULL
or0
into the column, or is an explicit nonspecial value.In the case of a multiple-row
INSERT
statement,mysql_insert_id()
returns the first automatically generatedAUTO_INCREMENT
value that was successfully inserted.If no rows are successfully inserted,
mysql_insert_id()
returns 0.If an
INSERT ... SELECT
statement is executed, and no automatically generated value is successfully inserted,mysql_insert_id()
returns the ID of the last inserted row.If an
INSERT ... SELECT
statement usesLAST_INSERT_ID(
,expr
)mysql_insert_id()
returnsexpr
.INSERT
statements that generate anAUTO_INCREMENT
value by insertingLAST_INSERT_ID(
into any column or by updating any column toexpr
)LAST_INSERT_ID(
.expr
)If the previous statement returned an error, the value of
mysql_insert_id()
is undefined.
The return value of mysql_insert_id()
can be simplified to the following sequence:
If there is an
AUTO_INCREMENT
column, and an automatically generated value was successfully inserted, return the first such value.If
LAST_INSERT_ID(
occurred in the statement, returnexpr
)expr
, even if there was anAUTO_INCREMENT
column in the affected table.The return value varies depending on the statement used. When called after an
INSERT
statement:If there is an
AUTO_INCREMENT
column in the table, and there were some explicit values for this column that were successfully inserted into the table, return the last of the explicit values.
When called after an
INSERT ... ON DUPLICATE KEY UPDATE
statement:If there is an
AUTO_INCREMENT
column in the table and there were some explicit successfully inserted values or some updated values, return the last of the inserted or updated values.
mysql_insert_id()
returns 0
if the previous statement does not use an AUTO_INCREMENT
value. If you must save the value for later, be sure to call mysql_insert_id()
immediately after the statement that generates the value.
The value of mysql_insert_id()
is affected only by statements issued within the current client connection. It is not affected by statements issued by other clients.
The LAST_INSERT_ID()
SQL function will contain the value of the first automatically generated value that was successfully inserted. LAST_INSERT_ID()
is not reset between statements because the value of that function is maintained in the server. Another difference from mysql_insert_id()
is that LAST_INSERT_ID()
is not updated if you set an AUTO_INCREMENT
column to a specific nonspecial value. See Section 12.15, “Information Functions”.
mysql_insert_id()
returns 0
following a CALL
statement for a stored procedure that generates an AUTO_INCREMENT
value because in this case mysql_insert_id()
applies to CALL
and not the statement within the procedure. Within the procedure, you can use LAST_INSERT_ID()
at the SQL level to obtain the AUTO_INCREMENT
value.
The reason for the differences between LAST_INSERT_ID()
and mysql_insert_id()
is that LAST_INSERT_ID()
is made easy to use in scripts while mysql_insert_id()
tries to provide more exact information about what happens to the AUTO_INCREMENT
column.
The OK packet used in the client/server protocol holds information such as is used for session state tracking. When clients read the OK packet to know whether there is a session state change, this resets values such as the last insert ID and the number of affected rows. Such changes cause mysql_insert_id()
to return 0 after execution of commands including but not necessarily limited to COM_PING
, COM_REFRESH
, and COM_INIT_DB
.
A user-specified
AUTO_INCREMENT
value in a multiINSERT
statement falls within the range between the currentAUTO_INCREMENT
value and the sum of the current and number of rows affected values.