PostgreSQL CASE usage in functions

This concerns the conditional control structure CASE of the procedural language PL/pgSQL, to be used in plpgsql functions or DO statements.
Not to be confused with the CASE expression of SQL. Different language! And subtly different syntax rules, too.

While SQL CASE can be embedded in SQL expressions inside PL/pgSQL code (which is mostly just glue for SQL commands), you cannot have stand-alone SQL CASE expressions (would be nonsense).

-- inside plpgsql code block:CASE    WHEN old.applies_to = 'admin' THEN      _applies_to := 'My Self';   ELSE      _applies_to := initcap(old.applies_to);END CASE;

You have to use fully qualified statements, terminated with semicolon (;) and END CASE to close it.

Answer to additional question in comment

According to documentation the ELSE keyword of a CASE statement is not optional. I quote from the link above:

If no match is found, the ELSE statements are executed; but if ELSE is not present, then a CASE_NOT_FOUND exception is raised.

However, you can use an empty ELSE:

CASE    WHEN old.applies_to = 'admin' THEN      _applies_to := 'My Self';   ELSE      --  do nothingEND CASE;

This is different from SQL CASE expressions where ELSE is optional, but if the keyword is present, an expression has to be given, too!