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I have a case where i have to fetch records for column field1='value1' if there are no values for 'value1' then i should fetch the record for 'default'.
For the above scenario I have used two queries:
Select * from table_name where field1="value1"
If the above query does not give back any record I fire the following query:
Select * from table_name where field1="default"
Now I want to do the above stated in one query. Can someone please help me with the same. I believe the answer lies somewhere in using CASE WHEN clause.
Also the above queries should work for oracle, postgres as well as mysql.
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The CONVERT() function in SQL server is used to convert a value of one type to another type. It is the target data type to which the to expression will be converted, e.g: INT, BIT, SQL_VARIANT, etc. It provides the length of the target_type. Length is not mandatory.
The IN operator allows you to specify multiple values in a WHERE clause. The IN operator is a shorthand for multiple OR conditions.
It is possible to replace HAVING with WHERE, but there is no benefit in doing so.
You can specify multiple conditions in a single WHERE clause to, say, retrieve rows based on the values in multiple columns. You can use the AND and OR operators to combine two or more conditions into a compound condition. AND, OR, and a third operator, NOT, are logical operators.
Core ANSI SQL answer, expected to run on all different platforms:
select * from table_name
where field1 = 'value1'
or (field1 = 'default'
and NOT EXISTS (select 1 from table_name where field1 = 'value1'))
Use CASE and Exists like below
Select * from table_name where field1=
case when exists(select 1 from table_name where field1='value1')
then 'value1' else 'default 'end
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