Making the Move from Sybase to SQL Server
Optimizer Hints
MSSQL Server allows for optimizer hints on SELECT, INSERT, UPDATE, and DELETE statements. Sybase allows optimizer hints only on SELECT statements.
The MSSQL Server vs. Sybase GUI approach:
|
Sybase |
SQL Server |
| Use a text-based query analysis tool called SHOWPLAN | Use Query Analyzer |
| Command to enable SHOWPLAN from within ISQL
SET SHOWPLAN ON |
Command to enable SHOWPLAN_ALL or SHOWPLAN_TEXT from query analyzer
SET SHOWPLAN_ALL |
Temporary Table Names
|
Type of table name |
Maximum length |
| SQL Server table name |
128 |
| SQL Server temporary table name |
116 |
| Sybase table name |
30 |
| Sybase temporary table name |
13 |
Data Types
|
Data types |
Sybase |
SQL Server |
| char(n) |
255 |
8000 |
| varchar(n) |
255 |
8000 |
| nchar(n) |
255 |
4000 |
| nvarchar(n) |
255 |
4000 |
| binary |
255 |
8000 |
| varbinary |
255 |
8000 |
Notes:
1) The bit data type in MSSQLServer can be set to 0, 1, or NULL.
2) The bit data type in Sybase does not allow nulls.
Identity Columns
|
Sybase |
SQL Server |
|
Numeric(x,0) |
Tinyint,smallint,int,decimal(x,0) or numeric(x,0) |
Print Syntax
All PRINT statements that use substitution syntax must be changed to RAISERROR statements during the conversion process.
Conclusion
Converting a Sybase to SQL Server is a feat that can be accomplished, but there are a number of differences between the two products that must be addressed. Depending on the size of your application, this conversion could turn into a lengthy process. You don’t have to rewrite the whole application, but there are a fair amount of show stoppers. However, look at the bright side: I can’t think of an easier conversion between two major database packages than this one, and a successful conversion is highly probable because of the products many similarities. Happy migrating.
Published with the express written permission of the author. Copyright 2003.
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