Aggregate Function Descriptions If the argument size exceeds 511 bytes, an  ER_INVALID_BITWISE_AGGREGATE_OPERANDS_SIZE error occurs. Numeric evaluation produces an unsigned 64-bit integer. If there are no matching rows,  BIT_OR()  returns a neutral value (all bits set to 0) having the same length as the argument values. NULL  values do not affect the result unless all values are  NULL . In that case, the result is a neutral value having the same length as the argument values. For more information discussion about argument evaluation and result types, see the introductory discussion in Section 12.13, “Bit Functions and Operators” . If  BIT_OR()  is invoked from within the  mysql  client, binary string results display using hexadecimal notation, depending on the value of the  --binary-as-hex . For more information about that option, see Section 4.5.1, “mysql — The MySQL Command-Line Client” . As of MySQL 8.0.12, this function executes as a window function if  over_clause  is present. over_clause  is as described in Section 12.21.2, “Window Function Concepts and Syntax” . • BIT_XOR( expr ) [ over_clause ] •Binary-string evaluation produces a binary string of the same length as the argument values. If argument values have unequal lengths, an  ER_INVALID_BITWISE_OPERANDS_SIZE  error occurs. If the argument size exceeds 511 bytes, an  ER_INVALID_BITWISE_AGGREGATE_OPERANDS_SIZE error occurs. Numeric evaluation produces an unsigned 64-bit integer. •Binary-string evaluation occurs when the argument values have a binary string type, and the argument is not a hexadecimal literal, bit literal, or  NULL  literal. Numeric evaluation occurs otherwise, with argument value conversion to unsigned 64-bit integers as necessary. Returns the bitwise  XOR  of all bits in  expr Returns the bitwise  XOR  of all bits in  expr . The result type depends on whether the function argument values are evaluated as binary strings or numbers: If there are no matching rows,  BIT_XOR()  returns a neutral value (all bits set to 0) having the same length as the argument values. NULL  values do not affect the result unless all values are  NULL . In that case, the result is a neutral value having the same length as the argument values. For more information discussion about argument evaluation and result types, see the introductory discussion in Section 12.13, “Bit Functions and Operators” . If  BIT_XOR()  is invoked from within the  mysql  client, binary string results display using hexadecimal notation, depending on the value of the  --binary-as-hex . For more information about that option, see Section 4.5.1, “mysql — The MySQL Command-Line Client” . As of MySQL 8.0.12, this function executes as a window function if  over_clause  is present. over_clause  is as described in Section 12.21.2, “Window Function Concepts and Syntax” . • COUNT( expr ) [ over_clause ] If there are no matching rows,  COUNT()  returns  0 . Returns a count of the number of non- NULL  values of  expr  in the rows retrieved by a  SELECT statement. The result is a  BIGINT  value. 2397