What does @ mean in mysql

The @ symbol in MySQL has two uses: specifying variables (@variable name) and connecting table or column names (@table name or @column name), indicating the alias of a temporary or derived table in the database.

The meaning of @ symbol in MySQL

@ symbol has two main uses in MySQL:

1. Specify variables

@ symbol is used to specify variables, its syntax is:

<code>@变量名</code>

For example:

<code>SET @my_variable := 10;</code>

This will create a variable named @my_variable and set its value to 10.

2. Join table or column name

When the @ symbol is used with a table name or column name, it indicates that the object is a temporary or derived table in the database alias. This is typically used with temporary tables or stored procedures.

For example:

<code>SELECT * FROM table_name @alias;</code>

This will create an alias for the table_name table named @alias.

Note:

• Variable names are case-sensitive, but aliases are not case-sensitive.
• When specifying a variable, the @ symbol must follow the variable name without spaces.
• When specifying an alias, the @ symbol must precede the table name or column name.

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