Reputation: 2060
Imagine these tables structure
Organization table
=====================
| id | name |
-----+----------------+
| 1 | Organization 1 |
=====================
Place table
=================================
| id | name | organization_id |
-----+----------+-----------------+
| 1 | Place 1 | 1 |
-----+----------+-----------------+
| 2 | Place 2 | 1 |
-----+----------+-----------------+
| 3 | Place 3 | 1 |
=================================
Profile table
=============
| username |
--------------
| [email protected] |
--------------
| [email protected] |
=============
Visitedplace table
================================================
| id | place_id | profile_username | visiteddate |
-----+----------+---------------- -+-------------+
| 1 | 1 | [email protected] | 2017-01-01 |
-----+----------+------------------+-------------+
| 2 | 2 | [email protected] | 2017-02-01 |
-----+----------+------------------+-------------+
| 3 | 1 | [email protected] | 2017-01-15 |
================================================
Next are sql statments for creating tables and inserting data into it
-- ----------------------------
-- Table structure for organization
-- ----------------------------
DROP TABLE IF EXISTS "organization";
CREATE TABLE "organization" (
"id" int4 NOT NULL,
"name" varchar(255) COLLATE "default" NOT NULL
) WITH (OIDS=FALSE);
-- ----------------------------
-- Records of organization
-- ----------------------------
BEGIN;
INSERT INTO "organization" VALUES ('1', 'Organization 1');
COMMIT;
-- ----------------------------
-- Table structure for place
-- ----------------------------
DROP TABLE IF EXISTS "place";
CREATE TABLE "place" (
"id" int4 NOT NULL,
"name" varchar(255) COLLATE "default" NOT NULL,
"organization_id" int4 NOT NULL
)WITH (OIDS=FALSE);
-- ----------------------------
-- Records of place
-- ----------------------------
BEGIN;
INSERT INTO "place" VALUES ('1', 'Place 1', '1');
INSERT INTO "place" VALUES ('2', 'Place 2', '1');
INSERT INTO "place" VALUES ('3', 'Place 3', '1');
COMMIT;
-- ----------------------------
-- Table structure for profile
-- ----------------------------
DROP TABLE IF EXISTS "profile";
CREATE TABLE "profile" (
"username" varchar(255) COLLATE "default" NOT NULL
)WITH (OIDS=FALSE);
-- ----------------------------
-- Records of profile
-- ----------------------------
BEGIN;
INSERT INTO "profile" VALUES ('[email protected]');
INSERT INTO "profile" VALUES ('[email protected]');
COMMIT;
-- ----------------------------
-- Table structure for visitedplace
-- ----------------------------
DROP TABLE IF EXISTS "visitedplace";
CREATE TABLE "visitedplace" (
"id" int4 NOT NULL,
"place_id" int4 NOT NULL,
"profile_username" varchar(255) COLLATE "default" NOT NULL,
"visiteddate" date NOT NULL
)WITH (OIDS=FALSE);
-- ----------------------------
-- Records of visitedplace
-- ----------------------------
BEGIN;
INSERT INTO "visitedplace" VALUES ('1', '1', '[email protected]', '2017-02-24');
COMMIT;
-- ----------------------------
-- Alter Sequences Owned By
-- ----------------------------
-- ----------------------------
-- Primary Key structure for table organization
-- ----------------------------
ALTER TABLE "organization" ADD PRIMARY KEY ("id");
-- ----------------------------
-- Primary Key structure for table place
-- ----------------------------
ALTER TABLE "place" ADD PRIMARY KEY ("id");
-- ----------------------------
-- Primary Key structure for table profile
-- ----------------------------
ALTER TABLE "profile" ADD PRIMARY KEY ("username");
-- ----------------------------
-- Primary Key structure for table visitedplace
-- ----------------------------
ALTER TABLE "visitedplace" ADD PRIMARY KEY ("id");
-- ----------------------------
-- Foreign Key structure for table "place"
-- ----------------------------
ALTER TABLE "place" ADD FOREIGN KEY ("organization_id") REFERENCES
"organization" ("id") ON DELETE CASCADE ON UPDATE CASCADE;
------------------------------
-- Foreign Key structure for table "visitedplace"
-- ----------------------------
ALTER TABLE "visitedplace" ADD FOREIGN KEY ("profile_username") REFERENCES "profile" ("username") ON DELETE CASCADE ON UPDATE CASCADE;
ALTER TABLE "visitedplace" ADD FOREIGN KEY ("place_id") REFERENCES "place" ("id
") ON DELETE CASCADE ON UPDATE CASCADE;
My question is
When i run this next query
select profile.username, count(distinct place.id)
from profile profile
left outer join visitedplace visitedplace on profile.username=visitedplace.profile_username
inner join place place on visitedplace.place_id=place.id
where place.organization_id=1
group by profile.username
it return next result
=====================
| username | count |
-------------+-------
| [email protected] | 2 |
=====================
but i am expecting next result
=====================
| username | count |
-------------+-------
| [email protected] | 2 |
-------------+-------
| [email protected] | 0 |
=====================
So how can i do the query to return me what i am expecting?
I am using Postgres
Upvotes: 1
Views: 81
Reputation: 1269583
Use are using left join
. So, all joins should be outer joins (after the first one). And, you have to be careful about the where
clause:
select p.username, count(distinct place.id)
from profile p left outer join
visitedplace vp
on p.username = vp.profile_username left join
place pl
on vp.place_id = pl.id and pl.organization_id = 1
group by p.username;
If you are not careful, then the outer join turns into an inner join
.
Upvotes: 1