Up to this point, each example in this manual has consisted of an individual statement. You submit statements to Adaptive Server one at a time, entering the statement and receiving results interactively.
Adaptive Server can also process multiple statements submitted as a batch, either interactively or from a file. A batch or batch file is a set of Transact-SQL statements that are submitted together and executed as a group, one after the other. A batch is terminated by an end-of-batch signal. With the isql utility, this is the word “go” on a line by itself. For details on isql, see the Utility Guide.
Here is an example of a batch that contains two Transact-SQL statements:
select count(*) from titles select count(*) from authors go
Technically, a single Transact-SQL statement can constitute a batch, but it is more common to think of a batch as containing multiple statements. Frequently, a batch of statements is written to an operating system file before being submitted to isql.
Transact-SQL provides special keywords called control-of-flow language that allow the user to control the flow of execution of statements. Control-of-flow language can be used in single statements, in batches, in stored procedures, and in triggers.
Without control-of-flow language, separate Transact-SQL statements are performed sequentially, as they occur. Correlated subqueries, discussed in Chapter 5, “Subqueries: Using Queries Within Other Queries,” are a partial exception. Control-of-flow language permits statements to connect and to relate to each other using programming-like constructs.
Control-of-flow language, such as if...else for conditional performance of commands and while for repetitive execution, lets you refine and control the operation of Transact-SQL statements. The Transact-SQL control-of-flow language transforms standard SQL into a very high-level programming language.
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