I have something like this:
table1
ID NAME
table2
ID TABLE1_ID NAME VALUE
table3
ID TABLE2_ID COLLECTION
As you may be able to tell, multiple records from table2 can belong to a record in table1. table3 groups together multiple records in table2
It is no problem for me to loop through and display all of the table2 records for a given table1 record. How can I group those records based on table3 though.
May be by:
select * from table2 where id in (select table2_id from table3);
Related
This seems like it would be a simple setting, but I cannot find it. I do inner join queries on tables that have similar column names. It would be nice to include the table name in the query results, so the people receiving the data can differentiate more easily. For example:
Table1:
id
name
timestamp
Table2:
id
name
timestamp
table1_id
Table3:
id
name
timestamp
table2_id
Then I tie it all together with a query:
select * from table1
inner join table2 on table1.id=table2.table1_id
inner join on table2.id=table3.table2_id;
The results have similar column header names:
id name timestamp id name timestamp table1_id id name timestamp table2_id
It's hard to tell the data apart. Of course the example query is short and silly and pointless. If I do an actual query with all the data it get more complicated. Couldn't the column header name include the table name?
table1.id table1.name table1.timestamp table2.id table2.name table2.timestamp table2.table1_id table3.id table3.name table3.timestamp table3.table2_id
You have ambiguous column names in output: table1.id, table2.id
Adding alias for columns should solve this:
SELECT table1.id as t1_id, table2.id as t2_id
Instead of writing
select * from
you can write
select table1.id as table1_id,
and do the same for the other columns so that the results set would show you the names you give yourself for each column
You can use aliases to identify columns:
SELECT table1.id AS table1_id FROM ...
But you would have to do this for each field you want to select.
try this.hope it will help you.
SELECT table1.id as t1_id, table2.table1_id as t2_id
FROM tablename
inner join table2 on table1.id=table2.table1_id
inner join table3 on table2.id=table3.table2_id;
I have a table which contains unique names, call it table1. I have another table which contains the same names but each name occurs several times, call it table2. Now, I want to copy data from table2 to table1 corresponding to the names. And if table2 has multiple records by the same name, I want the corresponding new records to be created in table1.
TABLE1 TABLE2
NAME NAME
A A
B A
C B
D B
Following the little chat int he comments, you could try this:
UPDATE t1
set columnx = t2.columnx
FROM table1 t1
LEFT JOIN table2 t2 on t2.name = t1.name
WHERE t2.name is null
To achieve your full requirements, you may find it more useful to have multiple queries accomplish the one task.
In mysql, if I have a record that references the id of another record. For example
Table 1
id bigint
tabe2ref bigint
Table 2
id bigint
Where table2ref simply references Table2.id.
Is there a way to list all records in table 1 that reference a record in table 2 where that record doesn't exist?
If you want the data from table2 as well, use a LEFT JOIN as in dognose's answer. If you only want the data from table1, use a subquery, like this:
SELECT * FROM table1 WHERE table2ref NOT IN (
SELECT id FROM table2
)
Essentially, this reads "get everything from table 1 and subtract all rows which have a table2ref that isn't in all rows in table2."
You are looking for a LEFT JOIN - everything where the entry in table 2 is not existing will have a null for the table2.id after joining:
SELECT
table1.id, table1.table2ref, table2.id
FROM
table1
LEFT JOIN
table2
ON
table1.table2ref = table2.id
WHERE
ISNULL(table2.id) -- only those records with missing reference.
See also: http://giannopoulos.net/wp-content/uploads/2013/05/BHVicYICMAAdHGv.jpg
(first column, second row)
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
In table1 one of the fields is member_id.
In table2 one of the fields is member_username and the id field in this table is equal to the member_id field in table2.
The goal is to display all results from table1 in ascending alphabetical order based on member_username from table2.
Basically I need to resolve the member_id from table1 to a member_username from table2 and sort them alphabetically.
Any ideas?
You need to use a join from table1 to table2 to pick up the username, then sort on this field. You just need to be wary of a one-to-many relationship, i.e. if a member might have more than one entry in table2 with the same id you may get more rows than you expect.
select *
from table1
left join table2 on table2.id = table1.member_id
order by table2.member_username
If I didn't misunderstand your question, try joining both tables together and sort by member_username.
SELECT t1.*,
t2.member_username
FROM table1 AS t1
INNER JOIN table2 AS t2 ON t1.member_id = t2.id
ORDER BY t2.member_username ASC;
You can leave t2.member_username in the SELECT-part of the query, I just put it there for reference.