SQL variables, operators

One, variable

The SQL language, like other programming languages, has control statements such as variables, branches, loops, and so on.

In SQL language, variables are divided into local variables and global variables, and global variables are called system variables.

(i), local variables

Using The DECLARE keyword to declare a variable, the syntax is simple: DECLARE @< variable name > < variable type >

You can assign values to variables using the set keyword, and you can assign only one value to a variable at a time using the Set keyword.

We can also assign a value to this variable in a query statement.

(1),

(2), in the query statement

1.

2. No conditions

(b), global variables

Global variables: Also called system variables.

(1), view the number of affected rows

(2), using variable query

1.

2.

Second, operator

SQL variables, operators