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  1. MariaDB Server
  2. MDEV-8336

The meaning of NO_ZERO_DATE is not clear for DATETIME

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    Details

    • Type: Bug
    • Status: Closed (View Workflow)
    • Priority: Critical
    • Resolution: Fixed
    • Affects Version/s: 5.5, 10.1, 10.0
    • Fix Version/s: 10.1.6
    • Component/s: Temporal Types
    • Labels:
      None
    • Sprint:
      10.1.6-2

      Description

      The documentation days:

      The NO_ZERO_DATE mode affects whether the server permits '0000-00-00' as a valid date. Its effect also depends on whether strict SQL mode is enabled.

      But it does not say if DATETIME values with zero YYYYMMDD and non-zero hhmmss.uuuuuu parts (e.g. '0000-00 10:20:30') is permitted.

      Different parts of the code tread it differently for DATETIME.

      Example1: '0000-00-00 10:20:30' is not permitted

      SET sql_mode='NO_ZERO_DATE';
      SELECT TIMESTAMP'0000-00-00 10:20:30', TIMESTAMP'0000-00-01 10:20:30';

      returns

      +--------------------------------+--------------------------------+
      | TIMESTAMP'0000-00-00 10:20:30' | TIMESTAMP'0000-00-01 10:20:30' |
      +--------------------------------+--------------------------------+
      | NULL                           | 0000-00-01 10:20:30            |
      +--------------------------------+--------------------------------+
      1 row in set, 1 warning (0.00 sec)

      That is only the YYYYMMDD part is used to decide if the value is "ZERO DATE".

      Example2: '0000-00-00 10:20:30' behaves differently in the same script:

      SET sql_mode='NO_ZERO_DATE';
      DROP TABLE IF EXISTS t1; 
      CREATE TABLE t1 (a DATETIME);
      INSERT INTO t1 VALUES ('0000-00-00 10:20:30');
      SELECT a, LEAST(a,'2001-01-01 10:20:30') FROM t1;

      returns:

      +---------------------+--------------------------------+
      | a                   | LEAST(a,'2001-01-01 10:20:30') |
      +---------------------+--------------------------------+
      | 0000-00-00 10:20:30 | NULL                           |
      +---------------------+--------------------------------+
      1 row in set, 1 warning (0.00 sec)

      That is INSERT and "SELECT a FROM t1" treated '0000-00-00 10:20:30' as a permitted value, while LEAST() treated it as a non-permitted value.

      It should be fixed to treat in the same way in all context.

      Example3:

      SET sql_mode='NO_ZERO_DATE';
      SELECT STR_TO_DATE('0000-00-00 10:20:30','%Y-%m-%d %h:%i:%s');

      Example4:

      SET sql_mode='NO_ZERO_DATE';
      SELECT TIMESTAMP'0000-00-00 10:20:30';

      Exapmple 5:

      SET old_mode=zero_date_time_cast;
      SET SQL_MODE='NO_ZERO_DATE';
      SELECT CAST(TIME'10:20:30' AS DATETIME);

      Example 6:

      SET old_mode=zero_date_time_cast;
      SET SQL_MODE='NO_ZERO_DATE';
      SELECT CAST((CAST('10:20:30' AS TIME)) AS DATETIME);

      Example 7:

      SET old_mode=zero_date_time_cast;
      SET SQL_MODE='NO_ZERO_DATE';
      SELECT CAST((CAST(TIMESTAMP'0000-00-00 10:20:30' AS TIME)) AS DATETIME);

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            Assignee:
            bar Alexander Barkov
            Reporter:
            bar Alexander Barkov
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              Dates

              Created:
              Updated:
              Resolved: