Tutorial by Examples: coalesce

We can get a comma delimited string from multiple rows using coalesce as shown below. Since table variable is used, we need to execute whole query once. So to make easy to understand, I have added BEGIN and END block. BEGIN --Table variable declaration to store sample records DECLARE @...

COALESCE() returns the first NON NULL value in a list of arguments. Suppose we had a table containing phone numbers, and cell phone numbers and wanted to return only one for each user. In order to only obtain one, we can get the first NON NULL value. DECLARE @Table TABLE (UserID int, PhoneNumber va...

COALESCE () Evaluates the arguments in order and returns the current value of the first expression that initially does not evaluate to NULL. DECLARE @MyInt int -- variable is null until it is set with value. DECLARE @MyInt2 int -- variable is null until it is set with value. DECLARE @MyInt3 int -...

SELECT COALESCE(a, b, c, d, 5) FROM (SELECT NULL A, NULL b, NULL c, 4 d FROM DUAL); COALESCE(A,B,C,D,5)4 In some case, using COALESCE with two parameters can be faster than using NVL when the second parameter is not a constant. NVL will always evaluate both parameters. COALESCE will stop a...