mysql表达式(国外英语资料).docVIP

mysql表达式(国外英语资料) Expressions 1, expression form Expression: can be just a simple constant, such as numeric constant 0 and string constant ABC. Can be functions (function names and parentheses in the back); Syntax format: Select 1,helloworld; 2, MySQL operator 2.1 arithmetic operator Arithmetic operators include addition, subtraction, multiplication, division, and modulo operations. Note: if the divisor is 0, the illegal divisor is returned, and the result is NULL. You can use either% or MOD when picking up the die. Command: select 100/0; the division operation is when the divisor is 0. 2.2 logical operator A logical operator estimates an expression to determine whether it is true (non-zero) or false (zero). MySQL contains a C style and or || and non operator!, AND, OR, and NOT can also be replaced. Note that in ANSI SQL || as specified on the connector, but in MySQL, it represents a logical or operation. In MySQL, you must use CONCAT (ABC, def) to complete the connection of the string. Command: select, 10,ded||jjj, 1; Explanation: when performingded||jjjoperations, MySQL first convertsded to digits, converts the result to 0, convertsjjjto digits, and converts the result to 0, so the value of the expression is 0. 2.3 bit operator The bitwise operators have , or |, or ^, the left, right. 2.4 comparison operator Refer to the PPT 17 page chart. REGEXP - regular expression operator The most commonly used regular expression pattern characters are as follows: Match any single character; [[...]] matches any character in square brackets. A range of endpoints delimited by a short line - is specified and a character range is specified. For example, [0-9] means matching numbers from 0 to 9; Specify ^ as the first character of the interval. Represents a regular expression that matches from the first character; $ means the last character of the matching string, and if the regular expression is $, it means that it matches the end of the string. Frequency of regular expressions: