There a couple of ways you can do this, one by using the function ‘COALESCE’ and the other one is using CASE expression.

COALESCE is a simple function which takes one or more column names and a replacement (default) value which can be displayed in case of the missing data.  For example, in an employee table you want to display all the data of the column emp_first_name and in case there is no data present you want to display a constant value; no_first_name. Then the following query would help you achieve what you want.

SELECT COALESCE (emp_first_name,’no_first_name’)

FROM employee

In case you want to display emp_last_name (another column in employee table) with the missing data for emp_first_name, then run the query

SELECT COALESCE (emp_first_name, emp_last_name)

FROM employee

But there is a chance that both of them could be empty and you want to display something in case both missing then go for the following query.

SELECT COALESCE (emp_first_name, emp_last_name,’no_name’)

FROM employee

Another better and effective way to implement ‘IF THEN ELSE’ condition on the Select statement is to use the CASE expression. Following query would display the current date and if the current date is equal to ’2007/06/26′  then it would display the string ‘HI’ in case if the current date is not equal to ’2007/06/26′ then it would display ‘HELLO’. Try this out… 

SELECT (CASE date WHEN ’2007/06/26′ THEN ‘HI’ ELSE ‘HELLO’ END)

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