PREVIOUS VALUE FOR sequence_name
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Syntax
PREVIOUS VALUE FOR sequence_name
or
LASTVAL(sequence_name)
or in Oracle mode (SQL_MODE=ORACLE)
sequence_name.currval
Contents
PREVIOUS VALUE FOR
is IBM DB2 syntax while LASTVAL()
is PostgreSQL syntax.
Description
Get last value in the current connection generated from a sequence.
- If the sequence has not yet been used by the connection,
PREVIOUS VALUE FOR
returnsNULL
(the same thing applies with a new connection which doesn't see a last value for an existing sequence). - If a
SEQUENCE
has been dropped and re-created then it's treated as a newSEQUENCE
andPREVIOUS VALUE FOR
will returnNULL
. FLUSH TABLES
has no effect onPREVIOUS VALUE FOR
.- Previous values for all used sequences are stored per connection until connection ends.
PREVIOUS VALUE FOR
requires the SELECT privilege.
Example
CREATE SEQUENCE s START WITH 100 INCREMENT BY 10; SELECT PREVIOUS VALUE FOR s; +----------------------+ | PREVIOUS VALUE FOR s | +----------------------+ | NULL | +----------------------+ # The function works for sequences only, if the table is used an error is generated SELECT PREVIOUS VALUE FOR t; ERROR 4089 (42S02): 'test.t' is not a SEQUENCE # Call the NEXT VALUE FOR s: SELECT NEXT VALUE FOR s; +------------------+ | NEXT VALUE FOR s | +------------------+ | 100 | +------------------+ SELECT PREVIOUS VALUE FOR s; +----------------------+ | PREVIOUS VALUE FOR s | +----------------------+ | 100 | +----------------------+
Now try to start the new connection and check that the last value is still NULL, before updating the value in the new connection after the output of the new connection gets current value (110 in the example below). Note that first connection cannot see this change and the result of last value still remains the same (100 in the example above).
$ .mysql -uroot test -e"SELECT PREVIOUS VALUE FOR s; SELECT NEXT VALUE FOR s; SELECT PREVIOUS VALUE FOR s;" +----------------------+ | PREVIOUS VALUE FOR s | +----------------------+ | NULL | +----------------------+ +------------------+ | NEXT VALUE FOR s | +------------------+ | 110 | +------------------+ +----------------------+ | PREVIOUS VALUE FOR s | +----------------------+ | 110 | +----------------------+
See Also
- Sequence Overview
- CREATE SEQUENCE
- ALTER SEQUENCE
- NEXT VALUE FOR
- SETVAL(). Set next value for the sequence.
- AUTO_INCREMENT
- Information Schema SEQUENCES Table
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