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I want to add a column in a query that does not exist in a table and return it as a result. So lets say TABLE_TEST has column A, B and I want to return values for A, B and C. I am trying to do
SELECT A, B, C=3 FROM TABLE_TEST
or
SELECT *, C=3 FROM TABLE_TEST
Can this be done in MySQL, Postgresel or MSSQL?
665
You can add static value when you use INSERT INTO SELECT MySQL query. Write the value directly in the select statement or you can add with the help of variable which initializes the value. SET @yourVariableName − = yourstaticValue; INSERT INTO yourSecondTableName(yourColumnName1,yourColumnName2,....
Checking Existence of the Column:COL_LENGTH() function returns the defined length of a column in bytes. This function can be used with the IF ELSE condition to check if the column exists or not.
SQL NOT EXISTS in a subqueryNOT EXISTS is used with a subquery in the WHERE clause to check if the result of the subquery returns TRUE or FALSE. The Boolean value is then used to narrow down the rows from the outer select statement.
Yes, sure:
select a, b, 3 as c from table_test
That's it. It works on three db engines you've mentioned.
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