CASE 表达式;
DECODE 函数;
CASE expr
CASE expr WHEN compr_expr1 THEN rt_expr1 [WHEN compr_expr2 THEN rt_expr2 WHEN compr_expr3 THEN rt_expr3 ELSE else_expr] END
CASE 表达式;
DECODE 函数;
CASE expr
CASE expr WHEN compr_expr1 THEN rt_expr1 [WHEN compr_expr2 THEN rt_expr2 WHEN compr_expr3 THEN rt_expr3 ELSE else_expr] END