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.
]]>