advanced sql functions

By | January 9, 2020

Advanced SQL functions:


This function is used to return first non-NULL value from the list or from the table.

SELECT COALESCE(NULL, 1, 2, ‘’); –> Returns 1
SELECT COALESCE(NULL, 500, NULL, 200, ‘’); –> Returns 500
SELECT COALESCE(NULL, 77, ‘automation’, ‘’); –> returns 77
SELECT COALESCE(NULL, NULL, ‘automation’, ‘selenium99’); –> Returns automation
SELECT COALESCE (NULL,NULL,NULL,NULL,’selenium99′,700); –> Return below error.
Error: Conversion failed when converting the varchar value ‘selenium99’ to data type int.

Learn below operations with NULL:
7+NULL returns NULL only.
7*NULL returns NULL
TRUE and NULL return NULL but
TRUE or NULL returns TRUE.


CAST function is used to convert one datatype into a specified datatype.

CAST(100.1 AS varchar);
Result: 100.1 (varchar datatype)

CAST(100.1 AS varchar);
Result: 100 (int datatype)


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