postgresql 查询集合结果用逗号分隔返回字符串处理的操作

来源：jb51　　时间：2021/2/1 11:30:32　　对本文有异议

关键字：

string_agg('' , '')

例如：

select string_agg(name||'' , ',') from sys_user

补充：PostgreSQL 字段用逗号 “，”隔开判断是否含有某个值

Array Functions and Operators

https://www.postgresql.org/docs/9.2/functions-array.html

-- ----------------------------
-- Table structure for T_STUDENT
-- ----------------------------
DROP TABLE IF EXISTS "public"."T_STUDENT";
CREATE TABLE "public"."T_STUDENT" (
"id" int4,
"name" varchar(255) COLLATE "default",
"course" varchar(255) COLLATE "default"
)
WITH (OIDS=FALSE)
;
-- ----------------------------
-- Records of T_STUDENT
-- ----------------------------
INSERT INTO "public"."T_STUDENT" VALUES ('1', '李四', '12,45,1,66,7,89');
INSERT INTO "public"."T_STUDENT" VALUES ('2', '刘一', '1,5,8,9');
INSERT INTO "public"."T_STUDENT" VALUES ('3', '王五', '0,4,2');
INSERT INTO "public"."T_STUDENT" VALUES ('4', '张三', '1,2,5,7');
-- ----------------------------
-- Alter Sequences Owned By 
-- ----------------------------
-- ----------------------------
-- Table structure for T_STUDENT
-- ----------------------------
DROP TABLE IF EXISTS "public"."T_STUDENT";
CREATE TABLE "public"."T_STUDENT" (
"id" int4,
"name" varchar(255) COLLATE "default",
"course" varchar(255) COLLATE "default"
)
WITH (OIDS=FALSE)
;
-- ----------------------------
-- Records of T_STUDENT
-- ----------------------------
INSERT INTO "public"."T_STUDENT" VALUES ('1', '李四', '12,45,1,66,7,89');
INSERT INTO "public"."T_STUDENT" VALUES ('2', '刘一', '1,5,8,9');
INSERT INTO "public"."T_STUDENT" VALUES ('3', '王五', '0,4,2');
INSERT INTO "public"."T_STUDENT" VALUES ('4', '张三', '1,2,5,7');
-- ----------------------------
-- Alter Sequences Owned By 
-- ----------------------------
id name course
4	张三	1,2,5,7
1	李四	12,45,1,5,66,7,89
2	刘一	1,5,8,9
3	王五	0,4,2
SELECT * FROM "public"."T_STUDENT" WHERE string_to_array(course, ',') @> ARRAY['2','7']
结果：
id name course
4	张三	1,2,5,7
SELECT * FROM "public"."T_STUDENT" WHERE string_to_array(course, ',') <@ array['5','12','45','1','0','4','2']
结果：
id name course
3	王五	0,4,2
SELECT * FROM "public"."T_STUDENT" WHERE string_to_array(course, ',') && ARRAY['5','8','225','111']
结果：
id name course
4	张三	1,2,5,7
2	刘一	1,5,8,9