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MySQL in how to customize the function, many novices are not very clear about this, in order to help you solve this problem, the following editor will explain in detail for you, people with this need can come to learn, I hope you can gain something.

Control flow function

Case...when

The return value is judged according to the value, and the IF-ELSE judgment in analogical programming.

If (expr1,expr2,expr3)

If the expression expr1 is TRUE, the return value of IF () is expr2;, otherwise the return value is expr3.

Ifnull (expr1,expr2)

If the expression expr1 is not NULL, the return value is expr1; otherwise the return value is expr2.

Commonly used string function

CHAR_LENGTH ()

The return value is the length of the string.

CONCAT (str1...)

Concatenate concatenated strings.

ELT (NMagneStr1, str2, and...)

If Number1, the return value is str1, if Number2, the return value is str2, and so on, it can be used to transform the state of the returned page.

FORMAT (XBI D)

Format the numeric type.

TRIM (str)

Clear the string space.

Numerical function

FLOOR (X)

Returns the maximum integer value not greater than X.

MOD (NMagol M)

Module operation. Returns the remainder of N divided by M.

RAND () RAND (N)

Returns a random floating-point value ranging from 0 to 1. If an integer parameter N is specified, it is used as a seed value to generate repetitive sequences.

Time and date function

ADDDATE (date,INTERVALexprtype)

Give a specified date to operate on the specified type.

CURDATE ()

Returns the current date as a value in 'YYYY-MM-DD' or YYYYMMDD format, depending on whether the function is used in a string or numeric context.

DATE (expr)

Extract the date portion of the date or time date expression expr.

DATE_FORMAT (date,format)

Format the date value according to the format string.

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