I want to get the data from second table where the row id is equal to first table?Can any one help me with the syntax or code ?
There are a lot of different ways to do that.
You can use join:
Select t2.*
from tab2 t2
join tab1 t1 on t1.id = t2.id
also you can use in operator
Select *
from tab2 t2
where t2.id in ( select t1.id
from table1 t1
)
or you can use exists operator
Select *
from tab2 t2
where exists
(
selec 1
from table1 t1
where t2.id = t1.id
)
As your question is tagged with iPhone IOS so this may be the query string
NSString *query = [NSString stringWithFormat:#"SELECT * FROM secondTable WHERE rowid = %d",yourRowID];
//where yourRowID is your first table id
But if you're talking about Database syntax then see this link table joining .
Related
Say select id from some_expensive_query is the cte I want to share. Currently I write two sql in a transaction:
with t as (select id from some_expensive_query) select * from t1 join t on t.id =t1.id;
with t as (select id from some_expensive_query) select * from t2 join t on t.id =t2.id;
As you can see, the cte is executed twice but I want something like:
t = select id from some_expensive_query;
select * from t1 join t on t.id =t1.id;
select * from t2 join t on t.id =t2.id;
for portability, I don't want to use pgsql or functions, anyway to solve this?
Why don't you use union all ?
with t as (select id from some_expensive_query)
select * from t1 join t on t.id =t1.id
union all
select * from t2 join t on t.id =t2.id;
I have two tables in postgresql
One table is of the form
Create table table1(
ID serial PRIMARY KEY,
Type []Text
)
Create table table2(
type text,
sellerID int
)
Now i want to get all the rows from table1 which are having type same that in table2 but the problem is that in table1 the type is an array.
In case the type in the table has an identifiable delimiter like ',' ,';' etc. you can rewrite the query as regexp_split_to_table(type,',') or versions later than 9.5 unnest function can be use too.
For eg.,
select * from
( select id ,regexp_split_to_table(type,',') from table1)table1
inner join
select * from table2
on trim(table1.type) = trim(table2.type)
Another good example can be found - https://www.dbrnd.com/2017/03/postgresql-regexp_split_to_array-to-split-string-using-different-delimiters/
SELECT
a[1] AS DiskInfo
,a[2] AS DiskNumber
,a[3] AS MessageKeyword
FROM (
SELECT regexp_split_to_array('Postgres Disk information , disk 2 , failed', ',')
) AS dt(a)
You can use the ANY operator in the JOIN condition:
select *
from table1 t1
join table2 t2 on t2.type = any (t1.type);
Note that if the types in the table1 match multiple rows in table2, you would get duplicates (from table1) because that's how a join works. Maybe you want an EXISTS condition instead:
select *
from table1 t1
where exists (select *
from table2 t2
where t2.type = any(t1.type));
I want to copy rows from one table t2 to another t1, while excluding rows with values already existing in t1. The usual approach of 'NOT IN' works fine but only as long there are not multiple occurences of the same value in the source table t2.
Now, assuming I have two tables with the schema:
CREATE TABLE t1 ( id INTEGER );
CREATE TABLE t2 ( id INTEGER );
then insert data into them like:
INSERT INTO t1 VALUES (1);
INSERT INTO t2 VALUES (1);
INSERT INTO t2 VALUES (2);
Now, I try to insert all data from t2 into t1 but exclude pre-existing in t1:
INSERT INTO t1 (id) SELECT t2.id FROM t2
WHERE t2.id NOT IN ( SELECT t1.id FROM t1 WHERE t1.id = t2.id );
it works flawlessly; the row in t2 with the value of '1' did not get insert a second time into t1:
SELECT * FROM t1;
id
----
1
2
(2 rows)
But when there are multiple occurences of the same value in t2 it doesn't check if they exist in t1 for each individual insert, but for the whole transaction as it seems. Let's continue with my example by:
DELETE FROM t1;
INSERT INTO t2 VALUES (2);
SELECT * FROM t2;
id
----
1
2
2
(3 rows)
INSERT INTO t1 (id) SELECT t2.id FROM t2
WHERE t2.id NOT IN ( SELECT t1.id FROM t1 WHERE t1.id = t2.id );
SELECT * FROM t1;
id
----
1
2
2
(3 rows)
The same result is achieved with WHERE NOT EXISTS as well.
Has anyone an idea of how to check for existing values in t1 on an individual row-level to prevent multiple occurences?
I could as well use ON CONFLICT DO ... but I rather not want to since the idea is to split the data coming from t2 into a "clean" t1 and a "dirty" t1_faulty where all the rows are collected which do not fit some given criteria (one of which the uniqueness of id for which I am asking this question).
I think you could simply filter the records you want from the source table (t2).
you might use distinct on
INSERT INTO t1 (id) SELECT distinct on (t2.id) t2.id FROM t2
WHERE t2.id NOT IN ( SELECT t1.id FROM t1 WHERE t1.id = t2.id );
or group by
INSERT INTO t1 (id) SELECT t2.id FROM t2
WHERE t2.id NOT IN ( SELECT t1.id FROM t1 WHERE t1.id = t2.id ) group by t2.id;
or, if you want only the records that are already unique on t2, add a having count = 1
INSERT INTO t1 (id) SELECT t2.id FROM t2
WHERE t2.id NOT IN ( SELECT t1.id FROM t1 WHERE t1.id = t2.id )
group by t2.id
having count(t2.id) = 1
If I have a query
select * into #tmp1 from dbo.t1 inner join dbo.t2 on t1.Sender_Id=t2.Id
I get an error
Column names in each table must be unique. Column name 'Id' in table '#tmp1' is specified more than once.
How can I do the same thing without resorting to
select t1.Id as t1id, t1.col2. ... t1.col30, t2.Id as t2id, ... t2.col40 as t2col40 from ...
notation.
I just need to quickly and manualy examine several tables, so I'd like to have a quick way of examining joins.
If you have to persist the result via select * into #tmp or want to create a view, every field name has to be unique and you will have to uses aliases for fields with identical names.
A simple query does not need unique names.
Yes, columns name must unique in select statement, in your case, you have for example two (02) id, one from tbl1, and the other one from tbl2, on esolution is list them as:
Select t1.id, t2.id
From tbl1 as t1 Inner Join tbl2 as t2 on t1.id = t2.id
Hope this help.
Or, if you have columns with same name in both tables, use this:
Select t1.*, t2.* From tbl1 as t1 Inner join tbl2 as t2 On t1.id = t2.id
Regards
I wrote this, and it is wrong syntax, help me fix it, I want 'T' to be an alias of the result of the two inner joins.
select T.id
from table1
inner join table2 on table1.x = table2.y
inner join table3 on table3.z = table1.w as T;
You cannot use aliases to name the "entire" join, you can, however, put aliases on individual tables of the join:
select t1.id
from table1 t1
inner join table2 t2 on t1.x = t2.y
inner join table3 t3 on t3.z = t1.w
In the projection, you will have to use the alias of the table, which defines the id column you are going to select.
You can't directly name the result of a join. One option is to use a subquery:
select T.id
from (
select *
from table1
inner join table2 on table1.x = table2.y
inner join table3 on table3.z = table1.w
) T
Another option is subquery factoring:
with T as (
select *
from table1
inner join table2 on table1.x = table2.y
inner join table3 on table3.z = table1.w
)
select T.id
from T