I am new to postgresssql.
I have two table like this
Table A
id |value | type1 | type2 | type3
bigint |text | bigint | bigint | bigint
Table B
Id | description
bigint | text
Table A's type1,type2,type3 is the ids of Table B but not foreign key constraint.
I have to retrieve like this
Select a.id,
a.value,
b.description1(as of a.type1),
b.description1(as of a.type1),
b.description1(as of a.type1)
If you have to many columns you should consider change your db design
TableA
id | value
1 | <something>
2 | <something>
TableAType
id | TableA.id | type_id | typeValue
1 | 1 | type1 | bigint
2 | 1 | type2 | bigint
3 | 1 | type3 | bigint
.....
4 | 1 | typeN | bigint
TableB (type_description)
Id | description
bigint | text
Then your query become more simple and isn't affected when you add/remove types.
SELECT TB.Description, TT.TypeValue
FROM TableAType TT
JOIN TableB TB
ON TT.Type_id = TB.id
Then you can use a PIVOT to get the tabular data. Again the advantage is you can delete remove types, and your query doesnt change, only need update the types tables.
You should (LEFT) JOIN tableB 3 times, and use a different alias for each one.
select id, value,
type1, t1.description descri1,
type2, t2.description descri2,
type3, t3.description descri3
from tableA ta
left join tableB t1
on ta.type1 = t1.id
left join tableB t2
on ta.type2 = t2.id
left join tableB t3
on ta.type3 = t3.id;
Related
I have two tables
The first table contains three text fields(username, email, num) the second have only one column with random birth_date DATE.
I need to merge tables without condition
For example
first table:
+----------+--------------+-----------+
| username | email | num |
+----------+--------------+-----------+
| 'user1' | 'user1#mail' | '+794949' |
| 'user2' | 'user2#mail' | '+799999' |
+----------+--------------+-----------+
second table:
+--------------+
| birth_date |
+--------------+
| '2001-01-01' |
| '2002-02-02' |
+--------------+
And I need result like
+----------+------------+-------------+--------------+
| username | email | num | birth_date |
+----------+------------+-------------+--------------+
| 'user1' | 'us1#mail' | '+7979797' | '2001-01-01' |
| 'user2' | 'us2#mail' | '+79898998' | '2002-02-02' |
+----------+------------+-------------+--------------+
I need to get in result table with 100 rows too
Tried different JOIN but there is no condition here
Sure there is a join condition, about the simplest there is: Join on true or cross join. Either is the basic merge tables without condition. However this does not result in what you want as it generates a result set of 10k rows. But you an then use limit:
select *
from table1
join table2 on true
order by random()
limit 100;
select *
from table1
cross join table2
order by random()
limit 100;
There is other option, witch I think may be closer to what you want. Assign a value to each row of each table. Then join on this assigned value:
select <column list>
from (select *, row_number() over() rn from table1) t1
join (select *, row_number() over() rn from table2) t2
on (t1.rn = t2.rn);
To eliminate the assigned value you must specifically list each column desired in the result. But that is the way it should be done anyway.
See demo here. (demo user just 3 rows instead of 100)
I want to insert default rows into a result set if the LEFT JOIN is NULL.
For example if Jane has no roles, I want to return some default ones in the results.
A query like this will return the following:
SELECT * FROM employees LEFT OUTER JOIN roles ON roles.employee_id = employees.id
Employee ID | Employee Name | Role ID | Role Name
1 | John | 1 | Admin
1 | John | 2 | Standard
2 | Jane | NULL | NULL
I want to return:
Employee ID | Employee Name | Role ID | Role Name
1 | John | 1 | Admin
1 | John | 2 | Standard
2 | Jane | NULL | Admin
2 | Jane | NULL | Standard
Is there a good way to do this in PostgreSQL?
I think you're looking for
SELECT e.*, r.*
FROM employees e
JOIN roles r ON r.employee_id = e.id
UNION ALL
SELECT e.*, NULL, default_name
FROM employees e
JOIN (VALUES ('Admin'), ('Standard')) AS roles(default_name)
WHERE NOT EXISTS (
SELECT *
FROM roles r
WHERE r.employee_id = e.id
)
I don't think there's a (good) way around the UNION because a LEFT JOIN introduces only a single row per unmatched row. You might be able to lift out the join against the employees table though:
SELECT e.*, r.*
FROM employees e,
LATERAL (
SELECT r.id, r.name
FROM roles r
WHERE r.employee_id = e.id
UNION ALL
SELECT NULL, default_name
FROM (VALUES ('Admin'), ('Standard')) AS roles(default_name)
WHERE NOT EXISTS (
SELECT *
FROM roles r
WHERE r.employee_id = e.id
)
)
I'm Nubie.
I want to create a postgresql table by drawing data from several tables
Table1
| partner_id | **project_id** | partner_fund | partner_date |
| 12345 | 099 | 12345.70 | 2003-02-02 |
Table2
| partner_id | partner_name
| 12345 | monster.inc
Table3
| **package_id** | **project_id** |
| 099a | 099 |
Table4
| **package_id** | project_name
| 099a | kill some one
*package_id is corresponding to project_id
I want to make a table like this :
| (if)partner_id | (get)partner_name | (if)project_id (corresponding to package_id)| (get)project_name | partner_fund | partner_date
So, if first row shows partner_id, next column shows partner_name, etc. Please help. Thanks.
You can create a new table from a SELECT query using CREATE TABLE ... AS syntax:
CREATE TABLE new_table AS
SELECT
table1.partner_id,
table2.partner_name,
table3.project_id,
table3.project_name,
table1.partner_fund
FROM table1
INNER JOIN table2 ON (table1.partner_id = table2.partner_id)
INNER JOIN table3 ON (table1.project_id = table3.project_id)
;
...and then you can also add a primary key to the new table, e.g.:
ALTER TABLE new_table ADD PRIMARY KEY (partner_id, project_id);
Query after updated question:
CREATE TABLE new_table AS
SELECT
table1.partner_id,
table2.partner_name,
table1.project_id,
table4.project_name,
table1.partner_fund,
table1.partner_date
FROM table1
INNER JOIN table2 ON (table1.partner_id = table2.partner_id)
INNER JOIN table3 ON (table1.project_id = table3.project_id)
INNER JOIN table4 ON (table3.package_id = table4.package_id)
;
I have 2 tables that I need to join based on distinct rid while replacing the column value with having different values in multiple rows. Better explained with an example set below.
CREATE TABLE usr (rid INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
name VARCHAR(12) NOT NULL,
email VARCHAR(20) NOT NULL);
CREATE TABLE usr_loc
(rid INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
code CHAR NOT NULL PRIMARY KEY,
loc_id INT NOT NULL PRIMARY KEY);
INSERT INTO usr VALUES
(1,'John','john#product'),
(2,'Linda','linda#product'),
(3,'Greg','greg#product'),
(4,'Kate','kate#product'),
(5,'Johny','johny#product'),
(6,'Mary','mary#test');
INSERT INTO usr_loc VALUES
(1,'A',4532),
(1,'I',4538),
(1,'I',4545),
(2,'I',3123),
(3,'A',4512),
(3,'A',4527),
(4,'I',4567),
(4,'A',4565),
(5,'I',4512),
(6,'I',4567);
(6,'I',4569);
Required Result Set
+-----+-------+------+-----------------+
| rid | name | Code | email |
+-----+-------+------+-----------------+
| 1 | John | B | 'john#product' |
| 2 | Linda | I | 'linda#product' |
| 3 | Greg | A | 'greg#product' |
| 4 | Kate | B | 'kate#product' |
| 5 | Johny | I | 'johny#product' |
| 6 | Mary | I | 'mary#test' |
+-----+-------+------+-----------------+
I have tried some queries to join and some to count but lost with the one which exactly satisfies the whole scenario.
The query I came up with is
SELECT distinct(a.rid)as rid, a.name, a.email, 'B' as code
FROM usr
JOIN usr_loc b ON a.rid=b.rid
WHERE a.rid IN (SELECT rid FROM usr_loc GROUP BY rid HAVING COUNT(*) > 1);`
You need to group by the users and count how many occurrences you have in usr_loc. If more than a single one, then replace the code by B. See below:
select
rid,
name,
case when cnt > 1 then 'B' else min_code end as code,
email
from (
select u.rid, u.name, u.email, min(l.code) as min_code, count(*) as cnt
from usr u
join usr_loc l on l.rid = u.rid
group by u.rid, u.name, u.email
) x;
Seems to me that you are using MySQL, rather than IBM DB2. Is that so?
I'm having some hard time understanding what I'm doing wrong.
The result of this query shows the same results for each row instead of being updated by the right result.
My DATA
I'm trying to update a table of stats over a set of business
business_stats ( id SERIAL,
pk integer not null,
b_total integer,
PRIMARY KEY(pk)
);
the details of each business are stored here
business_details (id SERIAL,
category CHARACTER VARYING,
feature_a CHARACTER VARYING,
feature_b CHARACTER VARYING,
feature_c CHARACTER VARYING
);
and here a table that associate the pk with the category
datasets (id SERIAL,
pk integer not null,
category CHARACTER VARYING;
PRIMARY KEY(pk)
);
WHAT I DID (wrong)
UPDATE business_stats
SET b_total = agg.total
FROM business_stats b,
( SELECT d.pk, count(bd.id) total
FROM business_details AS bd
INNER JOIN datasets AS d
ON bd.category = d.category
GROUP BY d.pk
) agg
WHERE b.pk = agg.pk;
The result of this query is
| id | pk | b_total |
+----+----+-----------+
| 1 | 14 | 273611 |
| 2 | 15 | 273611 |
| 3 | 16 | 273611 |
| 4 | 17 | 273611 |
but if I run just the SELECT the results of each pk are completely different
| pk | agg.total |
+----+-------------+
| 14 | 273611 |
| 15 | 407802 |
| 16 | 179996 |
| 17 | 815580 |
THE QUESTION
why is this happening?
why is the WHERE clause not working?
Before writing this question I've used as reference these posts: a, b, c
Do the following (I always recommend against joins in Updates)
UPDATE business_stats bs
SET b_total =
( SELECT count(c.id) total
FROM business_details AS bd
INNER JOIN datasets AS d
ON bd.category = d.category
where d.pk=bs.pk
)
/*optional*/
where exists (SELECT *
FROM business_details AS bd
INNER JOIN datasets AS d
ON bd.category = d.category
where d.pk=bs.pk)
The issue is your FROM clause. The repeated reference to business_stats means you aren't restricting the join like you expect to. You're joining agg against the second unrelated mention of business_stats rather than the row you want to update.
Something like this is what you are after (warning not tested):
UPDATE business_stats AS b
SET b_total = agg.total
FROM
(...) agg
WHERE b.pk = agg.pk;