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CASE
Switch statement construct. There are two species of CASE statement. The first is a collection of independent “WHEN” conditions. The first to evaluate true returns its value. The second uses only one expression or condition, and returns the first “WHEN” clause which equals the expression.
Syntax
(CASE
WHEN condition THEN val1
WHEN condition THEN val2
...
ELSE defaultval END)
Switching off a single expression:
(CASE expression
WHEN case1 THEN val1
WHEN case2 THEN val2
...
ELSE defaultval END)
Arguments
- Any SQL objects
Return Type
The return type depends on the type of arguments val1, val2, etc. For example, if val1 or val2 is an integer, the return type will be an integer, depending on which condition is met. If they are both strings, the return type will be a string, and so on.
Examples
memsql> select (case
-> when 1=0 then 3
-> when 0=1 then 5
-> else 8 end) as choices;
+---------+
| choices |
+---------+
| 8 |
+---------+
1 row in set (0.21 sec)
memsql> select (case 'ohai'
-> when 'yo' then 'sup'
-> when 'hello' then 'hi'
-> when 'ohai' then 'bai'
-> else 'huh?' end) as greeting;
+----------+
| greeting |
+----------+
| bai |
+----------+
