I have two tables T1 and T2. I want to merge only those rows of T2 which is currently not there in T1 .
`Insert into T1 select * from (select * from T2 where id not in (select id from T1))`
Is there a better and faste way of achieving the same. ID column is unique across the table
Insert into T1
select * from T2
where id not in (select id from T1)
You could also join but then you'd need another subselect since MySQL does not want to select from a table it inserts at the same time without using a subselect.
Related
I have two table as table1 and table2 given below:
I want to have the value of only those table_name from table1 which has there id in print_table column in table 2.
I have implemented the following query but it returns only one value:
SELECT * FROM print_tabel_permission_admin WHERE id IN (select print_table from secondary)
Use FIND_IN_SET:
SELECT DISTINCT
t1.table_name
FROM table1 t1
INNER JOIN table2 t2
ON FIND_IN_SET(t1.id, t2.print_table) > 0;
Demo
You should probably move away from storing CSV data in your tables like this. Instead, break out the IDs in table2 onto separate rows. This will make your life easier.
I have an empty table (t1) and I want to insert or update the t1.uid column from another table's (t2) GROUP BY uid values.
So far I have tried like this:
UPDATE table1 t1 JOIN
(SELECT uid FROM table2 GROUP BY uid) t2
SET t1.uid = t2.uid;
but it's not working for me.
N.B. I've got a massive data set for which group by (uid from table-t2) results giving me total 1114732 results which I have to insert/update in t1 table's uid column.
Please try this:
Insert into table1(uid)
select distinct uid from table2
If table1 is empty, then UPDATE is not the correct verb. Would this suit your needs?
INSERT into table1 SELECT distinct uid from table2;
INSERT ... SELECT docs
I have a very big amount of data on my tables (table 1 and table 2) so I am asking this simple question because I want to have the most efficient way to do this:
How can I delete all the entries from table 1, which are also in table 2 (identified by attribute 'atribxy'). So there will be only exclusive entries in table 1 and in table 2. How can I achieve this in the most efficent way using a SQL-query?
There are many ways to do so:
Using JOIN
DELETE table2
FROM table2
INNER JOIN table1 ON table1.atribxy = table2.atribxy
Using IN
DELETE FROM table2 WHERE atribxy IN (SELECT atribxy FROM table1)
Using EXIST
DELETE FROM table2 t2 WHERE EXISTS ( SELECT 1 FROM table1 t1 WHERE t1.atribxy = t2.atribxy)
I have table_1 with unique records of IDs and multiple columns of data
and
table_2 with multiple rows concerning particular ID and multiple columns. One of the column in table2 is, say, time_lapse.
I need those two tables joined with all columns saved but with only those rows from table2 with highest time_lapse value.
I was trying this way...
create table as new_table
select table1.*, table2.* from
table1 left join table2
on table1.id=table2.id
where time_lapse=
(select max(time_lapse) from table2
group by id);
... but it failed.
Any suggestions for a newbie? Thank you.
You are close. But you are selecting the maximum time_lapse per id and then you act as if you had only selected one record with only one time_lapse. Use IN and have the id in the select list of your subquery:
create table as new_table
select table1.*, table2.* from
table1 left join table2
on table1.id=table2.id
where (table2.id, table2.time_lapse) in
(select id, max(time_lapse) from table2
group by id);
Then you are outer-joining table2, but want certain criteria on it in the WHERE clause. That doesn't work (as columns in outer-joined records are null).
The same query a tad prettier with a real outer join:
create table as new_table
select t1.*, t2.*
from table1 t1
left join table2 t2 on t1.id = t2.id
and (t2.id, t2.time_lapse) in
(select id, max(time_lapse) from table2 group by id);
I have 2 tables. I want to find out whether the values present in the first table is there in another table with a different field name.
Here is how it looks,
Table1
BillNo
43529179
43256787
35425676
25467778
24354758
45754748
Table2
BNo
113104808
25426577
268579679
2542135464
252525232
235263663
I have 137 records in table1 that needs to be checked against table2.
Instead of doing it one by one using the following command,
Select * from Table2 where BNo = '43529179';
This gives the result for just the mentioned value. Is there a way to check for all the values in a single query?
Thanks!
You can use a sub-select to compare against:
Select * from Table2 where BNo IN (SELECT BillNo FROM Table1);
That will "evalaute" to something like Select * from Table2 where BNo IN (113104808, 25426577, 268579679, 2542135464, 252525232, ...);
Join the tables, and check how many matching records there are:
select
count(*) as Matches
from
Table1 as t1
inner join Table2 as t2 on t2.BNo = t1.BillNo
You can also use a left join to pick out the records in table 1 that has no matching record in table 2:
select
t1.BillNo
from
Table1 as t1
left join Table2 as t2 on t2.BNo = t1.BillNo
where
t2.BNo is null