Logical Operators

Compared with the original MogDB, Dolphin has two new logical operators:

1. The && operator is added.
2. The || operator is added.

• &&

  Description: When b_compatibility_mode is set to TRUE, it indicates the logical AND operation. The supported types include Boolean, time, date, integer, floating point, and bit string. The truth table is as follows:

  a	b	Result of a && b
  TRUE	TRUE	TRUE
  TRUE	FALSE	FALSE
  TRUE	NULL	NULL
  FLASE	FALSE	FALSE
  FALSE	NULL	FALSE
  NULL	NULL	NULL

  The following table describes the processing of different input types.

  Data Type	Processing Method
  Boolean	The logical AND operation is performed according to the truth table.
  Integer	Only the zero value is converted to Boolean false, and other values are converted to Boolean true. Then, the logical AND operation is performed.
  Floating point	Only zero is converted to Boolean false, and other values are converted to Boolean true. Then, the logical AND operation is performed.
  Bit string	Only the all-0 value is converted to Boolean false, and other values are converted to Boolean true. Then, the logical AND operation is performed.
  Time	The conversion mode of the time type depends only on the hour part. When '00:xx:xx' is entered, the time type is converted to Boolean false. When 'yy:xx:xx' is entered, if yy is not 0, the time type is converted to Boolean true. Then, the logical AND operation is performed.
  Date	The conversion mode of the date type depends only on the year part. When '0000-xx-xx' is entered, the date type is converted to Boolean false. When 'yyyy-xx-xx' is entered, if yy is not 0, the date type is converted to Boolean true. Then, the logical AND operation is performed.

  Return type: Boolean

  Example:

  MogDB=# SELECT 1 && 1;
  ?column?
  ----------
         t
  (1 row)

• ||

  Description: When sql_mode is not set to 'pipes_as_concat', it indicates a logical OR operation. The supported types include Boolean, time, date, integer, floating point, and bit string. The truth table is as follows:

  a	b	Result of a || b
  TRUE	TRUE	TRUE
  TRUE	FALSE	TRUE
  TRUE	NULL	TRUE
  FLASE	FALSE	FALSE
  FALSE	NULL	NULL
  NULL	NULL	NULL

  The following table describes the processing of different input types.

  Data Type	Processing Method
  Boolean	The logical OR operation is performed according to the truth table.
  Integer	Only the zero value is converted to Boolean false, and other values are converted to Boolean true. Then, the logical OR operation is performed.
  Floating point	Only the zero value is converted to Boolean false, and other values are converted to Boolean true. Then, the logical OR operation is performed.
  Bit string	Only the all-0 value is converted to Boolean false, and other values are converted to Boolean true. Then, the logical OR operation is performed.
  Time	The conversion mode of the time type depends only on the hour part. When '00:xx:xx' is entered, the time type is converted to Boolean false. When 'yy:xx:xx' is entered, if yy is not 0, the time type is converted to Boolean true. Then, the logical OR operation is performed.
  Date	The conversion mode of the date type depends only on the year part. When '0000-xx-xx' is entered, the date type is converted to Boolean false. When 'yyyy-xx-xx' is entered, if yy is not 0, the date type is converted to Boolean true. Then, the logical OR operation is performed.

  Return type: Boolean

  Example:

  MogDB=# SELECT 0 || 0;
  ?column?
  ----------
         f
  (1 row)