Database development Basics-sql Server variables, operators, if, while

Variable:

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

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

Local variables:

Use Declare keyword to variable declaration, syntax is very simple:declare @< variable name > < variable type >

assigning values to variables can be used Set keyword, You can assign only one value to a variable at a time when you use the SET keyword.

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

Example:

Global variables: Also called system variables.

Examples of several system variables that are commonly used:

Variable Small exercise:

Exercises for defining variables:

A way to print single quotes in a printed string: two single quotes

Operator:

Practice:

Operator Precedence:

If...else ... statement:

Example:

Practice:

While statement:

Example:

W hile If nesting example:

Example of break in while :

Example of parsing each step of a loop print:

Case ... when ... Example:

Database development Basics-sql Server variables, operators, if, while