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I saw a query run in a log file on an application. and it contained a query like:
SELECT ID FROM CUST_ATTR49 WHERE 1=0 what is the use of such a query that is bound to return nothing?
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A query like this can be used to ping the database. The clause: WHERE 1=0. Ensures that non data is sent back, so no CPU charge, no Network traffic or other resource consumption. A query like that can test for: server availability.
The WHERE clause is used to filter records. It is used to extract only those records that fulfill a specified condition.
The reason you put the WHERE 1=2 clause in that SELECT INTO query is to create a field-copy of the existing table with no data. If you did this: select * into Table2 from Table1. Table2 would be an exact duplicate of Table1 , including the data rows.
If you have worked with SQL databases before, you might have come across the statement WHERE 1=1. It is a common statement that is used to return all the records from a given table. The statement where 1=1 in SQL means true. It is the same operation as running the select statement without the where clause.
This may be also used to extract the table schema from a table without extracting any data inside that table. As Andrea Colleoni said those will be the other benefits of using this.
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A query like this can be used to ping the database. The clause:
WHERE 1=0 Ensures that non data is sent back, so no CPU charge, no Network traffic or other resource consumption.
A query like that can test for:
WHERE 1=0 OR <condition>)
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