The SQL Coalesce function is used to return the first nonnull expression among its arguments.
Note: If all the arguments are null, then it returns null value.
SQL Coalesce Function Syntax
Coalesce(value1, value2, value3, ...)
SQL Coalesce Function Example
Table: Users
| UserId | userName | screenName |
|---|---|---|
| 203 | Mazojys | null |
| 204 | Jozzh | Lnanyo |
| 205 | null | Dfaafk |
| 206 | null | Srlkrt |
| 302 | Jssme | null |
Select userId and userName, if userName is null then select screenName as userName:
SELECT userId, Coalesce(userName, screenName) AS userName FROM Users
The result will look like:
| UserId | userName |
|---|---|
| 203 | Mazojys |
| 204 | Jozzh |
| 205 | Dfaafk |
| 206 | Srlkrt |
| 302 | Jssme |