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sql-servert-sqlsybasesqldatatypes

Sybase, data type

I have 2 queries:

(1) 

declare @m varchar  
set @m='10'  
select * from test where month=@m

(2)

declare @m varchar(2)  
set @m='10'  
select * from test where month=@m

Number of rows in result is different. In 2 variant more than in first. What is the reason could be?

Solution

  • That's because when you don't specify how many bytes the varchar variable can hold, the engines uses the default with is 1:

    When n isn't specified in a data definition or variable declaration statement, the default length is 1. If n isn't specified when using the CAST and CONVERT functions, the default length is 30.

    So, in the first case you have:

    select * from test where month=1

    and in the second:

    select * from test where month=10