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Tip of the Day
Language: SQL Server
Expertise: Beginner
Apr 7, 1999

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Table Name Substitution with a variable

Question:
I have data that is broken into multiple tables depending on the month. For example:

99jan table 99feb table

These tables are all built the same and are very large (each one has 500,000 rows).

I am writing a simple interactive script that prompts you "From what month do you want to see your query?" and accepts your answer into a variable. It then will pull information from the table you entered. How can I use a statement like:

'Select col1,col2 from '&variable' where ...

Answer:
Assuming you are using SQL Server, you can use "dynamic sql." This means that you can build up a string that contains the command you want to run and then tell SQL Server to execute the string. For example:


use pubs
go
declare @string char(120), @table char(30)
select @table = 'authors'
select @string = 'select * from ' + @table
exec (@string)

/* or you can even do this */
exec ('select * from ' + @table)
However, I question the need to create separate tables for just 500,000 rows apiece on SQL Server. I've had tables with more than 10 million records perform quite well.
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