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This article mainly explains the "MySQL system and custom functions, triggers, what is the use of", the article explains the content is simple and clear, easy to learn and understand, the following please follow the editor's ideas slowly in-depth, together to study and learn the "MySQL system and custom functions, triggers are what the use of" it!

I. the system encapsulates the function

MySQL has many built-in functions that can quickly solve some business requirements in development, including process control functions, numeric functions, string functions, date-time functions, aggregate functions, and so on. The functions commonly used in these classifications are listed below.

1. Control flow function

Case... When

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

-- DEMO 01SELECT CASE DATE_FORMAT (NOW (),'% Ymuri% mmi% d') WHEN '2019-12-29' THEN 'today' WHEN' 2019-12-28 'THEN' yesterday' WHEN '2019-12-30' THEN 'tommor' ELSE' Unknow' END;-- DEMO 02SELECT (CASE WHEN 1 > 0 THEN 'true' ELSE' false' END) AS result

If (expr1,expr2,expr3)

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

SELECT IF (1 > 2)

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