|
SQL Anywhere supports a large subset of Transact-SQL, which is the dialect of SQL supported by Sybase Adaptive Server Enterprise. This chapter describes compatibility of SQL between SQL Anywhere and Adaptive Server Enterprise.
The goals of Transact-SQL support in SQL Anywhere are as follows:
Application portability Many applications, stored procedures, and batch files can be written for use with both Adaptive Server Enterprise and SQL Anywhere databases.
Data portability SQL Anywhere and Adaptive Server Enterprise databases can exchange and replicate data between each other with minimum effort.
The aim is to write applications to work with both Adaptive Server Enterprise and SQL Anywhere. Existing Adaptive Server Enterprise applications generally require some changes to run on a SQL Anywhere database.
Transact-SQL support in SQL Anywhere takes the following form:
Many SQL statements are compatible between SQL Anywhere and Adaptive Server Enterprise.
For some statements, particularly in the procedure language used in procedures, triggers, and batches, a separate Transact-SQL statement is supported together with the syntax supported in previous versions of SQL Anywhere. For these statements, SQL Anywhere supports two dialects of SQL. In this chapter, those dialects are called Transact-SQL and Watcom-SQL.
A procedure, trigger, or batch is executed in either the Transact-SQL or Watcom-SQL dialect. You must use control statements from one dialect only throughout the batch or procedure. For example, each dialect has different flow control statements.
The following diagram illustrates how the two dialects overlap.
SQL Anywhere supports a very high percentage of Transact-SQL language elements, functions, and statements for working with existing data. For example, SQL Anywhere supports all of the numeric functions, all but one of the string functions, all aggregate functions, and all date and time functions. As another example, SQL Anywhere supports extended DELETE and UPDATE statements using joins.
Further, SQL Anywhere supports a very high percentage of the Transact-SQL stored procedure language (CREATE PROCEDURE and CREATE TRIGGER syntax, control statements, and so on) and many, but not all, aspects of Transact-SQL data definition language statements.
There are design differences in the architectural and configuration facilities supported by each product. Device management, user management, and maintenance tasks such as backups tend to be system-specific. Even here, SQL Anywhere provides Transact-SQL system tables as views, where the tables that are not meaningful in SQL Anywhere have no rows. Also, SQL Anywhere provides a set of system procedures for some of the more common administrative tasks.
This chapter looks first at some system-level issues where differences are most noticeable, before discussing data manipulation and data definition language aspects of the dialects where compatibility is high.
Some SQL statements supported by SQL Anywhere are part of one dialect, but not the other. You cannot mix the two dialects within a procedure, trigger, or batch. For example, SQL Anywhere supports the following statements, but as part of the Transact-SQL dialect only:
Transact-SQL control statements IF and WHILE
Transact-SQL EXECUTE statement
Transact-SQL CREATE PROCEDURE and CREATE TRIGGER statements
Transact-SQL BEGIN TRANSACTION statement
SQL statements not separated by semicolons are part of a Transact-SQL procedure or batch
Adaptive Server Enterprise does not support the following statements:
control statements CASE, LOOP, and FOR
SQL Anywhere versions of IF and WHILE
CALL statement
SQL Anywhere versions of the CREATE PROCEDURE, CREATE FUNCTION, and CREATE TRIGGER statements
SQL statements separated by semicolons
The two dialects cannot be mixed within a procedure, trigger, or batch. This means that:
You can include Transact-SQL-only statements together with statements that are part of both dialects in a batch, procedure, or trigger.
You can include statements not supported by Adaptive Server Enterprise together with statements that are supported by both servers in a batch, procedure, or trigger.
You cannot include Transact-SQL-only statements together with SQL Anywhere-only statements in a batch, procedure, or trigger.