Or Logical or There is a non-zero null Return 1, yes null return null，All 0 returns 0 Not or ! Logical non have null return null，If 0 returns 1, if not 0 returns 0Īnd or & Logic and have null return null，If 0 returns 0, if not 0 returns 1 Logical operator (Boolean) operator describe If at least one of the two values is NULL, the result of the comparison is NULLģ. If both are strings, the comparison is performed by string

(in the procedure, the two are generally not compared) If an integer a string, the string will be automatically converted to a number for comparison. If both are integers, the comparison is based on integer values Here we use ascii The codes are: a,A,0(97,65,48) Least Returns the minimum value for two or more parameters Grertest Returns the maximum value for two or more parameters Is not null Judge whether a value is not NULL #Note that '' can only be exactly reversed 2, Operator 1. Match contains a perhaps l Equialphabetic Select * from ly where name regexp 'han|li' Select * from ly where name regexp 'han+' contain an Select * from ly where name regexp 'han*' Match there han of Select * from ly where name regexp 'l.u' Select * from ly where name regexp '^sh' What does it end with Match the previous string at least n times and at most m times Matches any character that is not in parentheses Matches any character in the character set Matches the preceding character 1 or more times Matches zero or more characters before it MySQL regular expressions use the keyword regexp to specify the matching pattern of regular expressions 2. MySQL regular expressions usually match the required special strings in the records according to the specified matching pattern when retrieving database records.

Mysql regular expression not there