MySQL – default value for TIMESTAMP(3)

MySQL

My database is MySql 5.6.

I want to use CURRENT_TIMESTAMP as the default value an attribute which is type of TIMESTAMP(3).

But I get the error:

ERROR 1067 (42000): Invalid default value for 'updated'

I think it is because CURRENT_TIMESTAMP is only in precision of second.

How can I set current time as the default value for a timestamp with fractional part?

Best Answer

As per documentation on timestamp and datetime type columns:

If a TIMESTAMP or DATETIME column definition includes an explicit fractional seconds precision value anywhere, the same value must be used throughout the column definition.

This is permitted:
CREATE TABLE t1 (
  ts TIMESTAMP(6) DEFAULT CURRENT_TIMESTAMP(6) ON UPDATE CURRENT_TIMESTAMP(6)
);

Other Examples:

mysql> create table tbl_so_q23671222_1( ts timestamp(3) default now() );
ERROR 1067 (42000): Invalid default value for 'ts'

mysql> create table tbl_so_q23671222_1( ts timestamp(3) default now(3) );
Query OK, 0 rows affected (0.59 sec)

mysql> create table tbl_so_q23671222_2( ts timestamp(3) default current_timestamp );
ERROR 1067 (42000): Invalid default value for 'ts'

mysql> create table tbl_so_q23671222_2( ts timestamp(3) default current_timestamp(3) );
Query OK, 0 rows affected (0.38 sec)

mysql> desc tbl_so_q23671222_1;
+-------+--------------+------+-----+----------------------+-------+
| Field | Type         | Null | Key | Default              | Extra |
+-------+--------------+------+-----+----------------------+-------+
| ts    | timestamp(3) | NO   |     | CURRENT_TIMESTAMP(3) |       |
+-------+--------------+------+-----+----------------------+-------+
1 row in set (0.01 sec)

mysql> desc tbl_so_q23671222_2;
+-------+--------------+------+-----+----------------------+-------+
| Field | Type         | Null | Key | Default              | Extra |
+-------+--------------+------+-----+----------------------+-------+
| ts    | timestamp(3) | NO   |     | CURRENT_TIMESTAMP(3) |       |
+-------+--------------+------+-----+----------------------+-------+
1 row in set (0.01 sec)

Refer to:
Initialization and Updating for TIMESTAMP and DATETIME

Related Solutions

Mysql – How to set a default value for a MySQL Datetime column

IMPORTANT EDIT: It is now possible to achieve this with DATETIME fields since MySQL 5.6.5, take a look at the other post below...

Previous versions can't do that with DATETIME...

But you can do it with TIMESTAMP:

mysql> create table test (str varchar(32), ts TIMESTAMP DEFAULT CURRENT_TIMESTAMP);
Query OK, 0 rows affected (0.00 sec)

mysql> desc test;
+-------+-------------+------+-----+-------------------+-------+
| Field | Type        | Null | Key | Default           | Extra |
+-------+-------------+------+-----+-------------------+-------+
| str   | varchar(32) | YES  |     | NULL              |       | 
| ts    | timestamp   | NO   |     | CURRENT_TIMESTAMP |       | 
+-------+-------------+------+-----+-------------------+-------+
2 rows in set (0.00 sec)

mysql> insert into test (str) values ("demo");
Query OK, 1 row affected (0.00 sec)

mysql> select * from test;
+------+---------------------+
| str  | ts                  |
+------+---------------------+
| demo | 2008-10-03 22:59:52 | 
+------+---------------------+
1 row in set (0.00 sec)

mysql>

CAVEAT: IF you define a column with CURRENT_TIMESTAMP ON as default, you will need to ALWAYS specify a value for this column or the value will automatically reset itself to "now()" on update. This means that if you do not want the value to change, your UPDATE statement must contain "[your column name] = [your column name]" (or some other value) or the value will become "now()". Weird, but true. I am using 5.5.56-MariaDB

Mysql – Which MySQL data type to use for storing boolean values

For MySQL 5.0.3 and higher, you can use BIT. The manual says:

As of MySQL 5.0.3, the BIT data type is used to store bit-field values. A type of BIT(M) enables storage of M-bit values. M can range from 1 to 64.

Otherwise, according to the MySQL manual you can use BOOL or BOOLEAN, which are at the moment aliases of tinyint(1):

Bool, Boolean: These types are synonyms for TINYINT(1). A value of zero is considered false. Non-zero values are considered true.

MySQL also states that:

We intend to implement full boolean type handling, in accordance with standard SQL, in a future MySQL release.

References: http://dev.mysql.com/doc/refman/5.5/en/numeric-type-overview.html

Best Answer

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