postgresql:字符串求和（拼接）详解数据库

--创建测试表 
DROP TABLE IF EXISTS test; 
CREATE TEMP TABLE test("Id" int,"Name" varchar(100),"Type" int); 
INSERT INTO test("Id","Name","Type")VALUES(1,'NO1',1),(2,'NO2',2),(3,'NO3',2),(4,'NO4',2),(5,'NO5',3),(6,'NO6',3); 
 
--将结果转换为数组 
--SELECT array(SELECT "Name" FROM test) 
 
--将数组合并为字符串 
--select array_to_string(array[1,2,3], ',') 
 
--合并后的结果 
--SELECT array_to_string(array(SELECT "Name" FROM test), ',') 
 
SELECT "Type" ,( array_to_string(array(SELECT "Name" FROM test as t WHERE t."Type" = test."Type" ) , ',') )  FROM test GROUP BY "Type";

DROP TABLE test;