This chapter describes the constructs in the MySQL language that control the scope and flow of execution.
In MySQL, as in all block-structured languages, groups of statements may be grouped together into blocks . A block can normally occur whenever a single statement would be permitted, and the block may contain its own distinct variable, cursor, and handler declarations.
The MySQL stored program language supports two types of stored
program control statements: conditional control statements and iteration
(looping) statements. Almost every piece of code you write requires
conditional control, which is the ability to direct the flow of
execution through your program based on a condition. You do this with
Iterative control structures—otherwise known as loops—let you execute the same code repeatedly. MySQL provides three different kinds of loop constructs:
Continues until you issue a
LEAVE statement to terminate the
Continues until an expression evaluates as true
Continues as long as an expression evaluates as true