Introduction to SQL Programming

One: SQL is also a programming language that you can use to program

Second: basic general programming elements

variables, operators, expressions, process controls, functions

Variable:

Typically, a field name is a variable name, and a field is a variable!

Special variables, such as system built-in variables (character_set_xxx, autocommit)

Typical operation of a variable: Assign value, get value!

User-defined variables:

User-defined variables need to be prefixed with @ as the variable name to differentiate whether the system built-in variable

Set statement; Can complete the setting of the variable

Set Variable name = variable Value

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How to get it?

You can use the SELECT statement!

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Implementation of Programming:

There are three ways of programming: triggers, stored functions, stored procedures

Function:

For MySQL, there are built-in functions

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Rand (), generate random number function, get random number between 0-1

Need to be used in conjunction with rounding

Floor (), rounding down

substring (string, position, length), intercept string function

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Note: Subscript starting at 1, and in number of characters:

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Char_length () Number of characters

Length () bytes

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Convert (string using character set) character to the corresponding target character set

Introduction to SQL Programming