IF...THEN...END IF

teledb=# CREATE OR REPLACE PROCEDURE p_if() AS
$$  
BEGIN         
    IF random()>0.5 THEN
        RAISE NOTICE '随机数大于0.5';
    END IF;
END;
$$
LANGUAGE plpgsql;
CREATE PROCEDURE
teledb=# CALL p_if();
NOTICE:  随机数大于0.5
CALL
teledb=#

..THEN...ELSE...END IF

teledb=# CREATE OR REPLACE PROCEDURE p_if_else() AS
$$  
BEGIN         
    IF random()>0.99 THEN
        RAISE NOTICE '随机数大于0.99';
    ELSE
        RAISE NOTICE '随机数小于或等于0.99';
    END IF;
END;
$$
LANGUAGE plpgsql;
CREATE PROCEDURE
teledb=# CALL p_if_else();
NOTICE:  随机数小于或等于0.99
CALL
teledb=#

IF...THEN...ELSIF...THEN...ELSE...END IF

teledb=# CREATE OR REPLACE PROCEDURE p_if_elsif()  AS
$$  
DECLARE
    v_float8 float8 := random();
BEGIN         
    IF v_float8>0.99 THEN
        RAISE NOTICE '随机数大于0.99';
    ELSIF v_float8>0.5 THEN
        RAISE NOTICE '随机数大于0.50';   
    ELSIF v_float8>0.25 THEN
        RAISE NOTICE '随机数大于0.25';     
    ELSE
        RAISE NOTICE '随机数小于或等于0.25';
    END IF;
END;
$$
LANGUAGE plpgsql;
CREATE PROCEDURE
teledb=# CALL p_if_elsif();
NOTICE:  随机数大于0.50
CALL

CASE 语句

teledb=# CREATE OR REPLACE PROCEDURE p_case()  AS
$$  
DECLARE
    v_float8 float8 := random();
BEGIN         
    CASE 
    WHEN v_float8>0.99 THEN
        RAISE NOTICE '随机数大于0.99';
    WHEN v_float8>0.5 THEN
        RAISE NOTICE '随机数大于0.50';   
    WHEN v_float8>0.25 THEN
        RAISE NOTICE '随机数大于0.25';     
    ELSE
        RAISE NOTICE '随机数小于或等于0.25';
    END CASE;
END;
$$
LANGUAGE plpgsql;
CREATE PROCEDURE
teledb=# CALL p_case();
NOTICE:  随机数小于或等于0.25
CALL
teledb=#