IF...THEN...END IF

teledb=# CREATE OR REPLACE FUNCTION f26() RETURNS VOID AS
teledb-# $$  
teledb$# BEGIN         
teledb$#     IF random()>0.5 THEN
teledb$#         RAISE NOTICE '随机数大于0.5';
teledb$#     END IF;
teledb$# END;
teledb$# $$
teledb-# LANGUAGE plpgsql;
CREATE FUNCTION
teledb=# select f26();
NOTICE:  随机数大于0.5
 f26 
-----
(1 row)
teledb=# 

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

teledb=# CREATE OR REPLACE FUNCTION f26() RETURNS VOID AS
teledb-# $$  
teledb$# BEGIN         
teledb$#     IF random()>0.99 THEN
teledb$#         RAISE NOTICE '随机数大于0.99';
teledb$#     ELSE
teledb$#         RAISE NOTICE '随机数小于或等于0.99';
teledb$#     END IF;
teledb$# END;
teledb$# $$
teledb-# LANGUAGE plpgsql;
CREATE FUNCTION
teledb=# select f26();
NOTICE:  随机数小于或等于0.99
 f26 
-----
(1 row)
teledb=#

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

teledb=# CREATE OR REPLACE FUNCTION f26() RETURNS VOID AS
teledb-# $$  
teledb$# DECLARE
teledb$#     v_float8 float8 := random();
teledb$# BEGIN         
teledb$#     IF v_float8>0.99 THEN
teledb$#         RAISE NOTICE '随机数大于0.99';
teledb$#     ELSIF v_float8>0.5 THEN
teledb$#         RAISE NOTICE '随机数大于0.50';   
teledb$#     ELSIF v_float8>0.25 THEN
teledb$#         RAISE NOTICE '随机数大于0.25';     
teledb$#     ELSE
teledb$#         RAISE NOTICE '随机数小于或等于0.25';
teledb$#     END IF;
teledb$# END;
teledb$# $$
teledb-# LANGUAGE plpgsql;
CREATE FUNCTION
teledb=# SELECT f26();
NOTICE:  随机数大于0.50
 f26 
-----
(1 row)

CASE 语句

teledb=# CREATE OR REPLACE FUNCTION f26() RETURNS VOID AS
teledb-# $$  
teledb$# DECLARE
teledb$#     v_float8 float8 := random();
teledb$# BEGIN         
teledb$#     CASE 
teledb$#     WHEN v_float8>0.99 THEN
teledb$#         RAISE NOTICE '随机数大于0.99';
teledb$#     WHEN v_float8>0.5 THEN
teledb$#         RAISE NOTICE '随机数大于0.50';   
teledb$#     WHEN v_float8>0.25 THEN
teledb$#         RAISE NOTICE '随机数大于0.25';     
teledb$#     ELSE
teledb$#         RAISE NOTICE '随机数小于或等于0.25';
teledb$#     END CASE;
teledb$# END;
teledb$# $$
teledb-# LANGUAGE plpgsql;
CREATE FUNCTION
teledb=# SELECT f26();
NOTICE:  随机数大于0.50
 f26 
-----
(1 row)