IF - ELIF - ELSE 结构

图: 比较两个参数的 IF - ELIF - ELSE 结构。

CREATE FUNCTION str_compare( str1 CHAR(20), str2 CHAR(20))
            RETURNING INTEGER;
            
            DEFINE result INTEGER;
            
            IF str1 > str2 THEN
            LET result = 1;
            ELIF str2 > str1 THEN
            LET result = -1;
            ELSE
            LET result = 0;
            END IF
            RETURN result;
            END FUNCTION;

图: 定义 manager 表。

CREATE TABLE manager
          (
          mgr_name   VARCHAR(30),
          department VARCHAR(12),
          dept_no    SMALLINT,
          direct_reports SET( VARCHAR(30) NOT NULL ),
          projects LIST( ROW ( pro_name VARCHAR(15),
          pro_members SET( VARCHAR(20) NOT NULL ) )
          NOT NULL),
          salary     INTEGER,
          );

图: 检查 SET 中元素数的 IF - ELIF - ELSE 结构。

CREATE FUNCTION checklist( d SMALLINT )
            RETURNING VARCHAR(30), VARCHAR(12), INTEGER;
            
            DEFINE name VARCHAR(30);
            DEFINE dept VARCHAR(12);
            DEFINE num INTEGER;
            
            SELECT mgr_name, department,
            CARDINALITY(direct_reports) 
            FROM manager INTO name, dept, num
            WHERE dept_no = d;
            IF num > 20 THEN
            EXECUTE FUNCTION add_mgr(dept);
            ELIF num = 0 THEN
            EXECUTE FUNCTION del_mgr(dept);
            ELSE
            RETURN name, dept, num;
            END IF;
            
            END FUNCTION;