Sybase Process Control

1. Variable Declaration and assignment

Global variables are predefined by the system and begin with the symbol @@ 打头

A local variable declaration uses the Declare statement, which must begin with a symbol @ followed by an identifier.

Declare @ variable name data type [, @ variable name data type, ...]

Variable assignment using the SELECT statement, the value of the unassigned variable is null.

Example:

Declare @msg Char (50)

Select @msg = ' How are '

Select @msg =emp_name from employee

Where emp_id=12345678

2. SQL statement block

Begin

Statement block/* SQL statements executed in multiple sequential order * *

End

3. Conditional statement

An If condition expression

Statement (block)

Else

Statement (block)

Example:

if (select Max (id) from sysobjects) <50

No user-created object in print ' Database

Else

Select Name,type,id from sysobjects where id>50

4. Loop statement

While condition expression

Statement (block)

Two special circular control statements:

Continue Execute Next loop

Break Exit Current Loop

Example:

while (select Avg. (price) from titles) >$20

Begin

Update titles Set PRICE=PRICE/2

If (select AVG (price) from titles) <$40

Break

Else

Continue

End

5. Other control statements

◇return Statement--an unconditional end to the current procedure and a State value that can be returned to the caller: return[integer expression]

◇print statement

◇raiseerror statement

◇waitfor statement