I have two tables with a VARCHAR column called "name1" and "name2":
table1:
id | name1
1 | xyz
2 | foo
3 | barfoo
4 | xchad
table2:
id | id_table1 | name2
1 | NULL | xchad
2 | NULL | foo
3 | NULL | hade
4 | NULL | bar
I want to update the column id_table1 of table2 with the respective id from table1 where the rows name1 and name2 match.
For example in table2 the first row should be updated with 4 in column id_table1 since 'xchad' = 'xchad'.
A join simply takes too much time with the string compare.
Thank you!
Consider:
UPDATE table1 t1
INNER JOIN table2 t2 ON t2.name2 = t1.name1
SET t2.id_table1 = t1.id
With indexes on table1(name1) and table2(name2), this should perform efficiently.
An alternative is to use a correlated subquery:
UPDATE table2 t2
SET t2.id_table1 = (
SELECT t1.name1 FROM table1 t1 WHERE t1.name1 = t2.id_table1
)
Please note that this second solution does require each name in table2 to have a unique match in table1.
Related
I have two tables.
table1:
| ID | NAME |
|----|------|
| 1 | aaa |
| 2 | aaa |
| 3 | aaa |
| 4 | bbb |
| 5 | bbb |
table2:
| ID | DATE |
|----|----------|
| 1 | 12/07/10 |
| 2 | 12/07/13 |
| 3 | 12/07/16 |
| 4 | 12/07/08 |
| 5 | 12/07/20 |
Help me pls, I don't know how to SELECT MAX ID in table1 by date in table2.
For example result should be:
for "aaa": ID 3 from table2
for "bbb": ID 5 from table2
I'm trying something like that:
DATE = (SELECT MAX(DATE) FROM table2 t2, table1 t1 WHERE t1.NAME = "aaa")
But it's not working... Have you got some idea?
You need to add an additional condition (t1.id = t2.id) for the join:
SELECT MAX(DATE)
FROM table2 t2, table1 t1
WHERE t1.NAME = "aaa"
AND t1.id = t2.id
But please - don't join with comma - use explicit JOIN syntax instead:
SELECT MAX(DATE)
FROM table2 t2
JOIN table1 t1
ON t1.id = t2.id
WHERE t1.NAME = "aaa"
You can also get all max dates for all names at once using GROUP BY name:
SELECT t1.NAME, MAX(t2.DATE)
FROM table2 t2
JOIN table1 t1
ON t1.id = t2.id
GROUP BY t1.NAME
I have tried to take the MAX Date using this query.
Note: In the table the date format should be (Y-m-d) and the field should be set to date in order to manipulate the operations
Table - 1(Name: test1)
Table - 2(Name: test2)
QUERY TO GET MAX FROM OTHER TABLE
SELECT MAX(dates) FROM test2 JOIN test1 WHERE test1.name='aaa'
OUTPUT
Hope so this query will solve your problem.
select ID from Table1 where date= (select max(date) from T2 where name= 'aaa'
i didn't fully got you. But I think this is how you want it.... If you had these two table as one table then it would work as charm.
Or THIS ,with Two Table like you asked for
SELECT T1.Id FROM T1 INNER JOIN T2
ON T1.Id = T2.Id
where T2.date = (select max(T2.date) from T1 where T1.name= 'aaa')
Is it possible in only one MySQL query to get the desired result (below) returned into one row ?
Where id=1 in Table 1
Table 1
|------|----------|----------|
| id | refIdOne | refIdTwo |
|------|----------|-----------
| 1 | 1 | 2 |
|------|----------|-----------
Columns "refIdOne" & "refIdTwo" refer Table 2 "id" column
Table 2
|------|------------------|
| id | text |
|------|------------------|
| 1 | cheese |
| 2 | made with milk |
|------|------------------|
Desired result returned in ONE ROW with custom AS columns named "subject" and "description" :
|----------|-----------------|
| subject | description |
|----------|-----------------|
| cheese | made with milk |
? Many thanks for help
* EDIT : Answer is *
select t21.text as subject, t22.text as description
from Table1 as t1
join Table2 as t21 on t1.refidone = t21.id
join Table2 as t22 on t1.refidtwo = t22.id
where t1.id = 1
Table2 has to joined twice to Table1.
select t21.text as subject, t22.text as description
from table1 t1
join table2 t21 on t1.refidone = t21.id
join table2 t22 on t1.refidtwo = t22.id
You need to perform Self join. Join Table2.ID twice with Table1.refIdOne and Table1.refIdTwo
select t2.text as subject, t3.text as description
from Table1 t1
Left join Table2 t2 on t1.refIdOne = t2.id
Left join Table2 t3 on t1.refIdTwo = t2.id
without joins
SELECT
(SELECT text FROM Table2 WHERE id = (SELECT refIdOne FROM Table1 WHERE id = 1) ) AS name,
(SELECT text FROM Table2 WHERE id = (SELECT refIdTwo FROM Table1 WHERE id = 1) ) AS description
I have two tables table1 and table2.
I'm doing some changes and I realized that table2 is not needed, but this table has lots of data already and I need to pass the values of ID_B from table2 to table1.
Here's the structure:
table1
ID_table1 | ID_table2 | ID_B
1 | 1 |
2 | 3 |
3 | 1 |
4 | 2 |
table2
ID_table2 | ID_B
1 | 14
2 | 26
3 | 26
So what I want is the MySQL query to pass the ID_B value from table2 to table1 when the ID_table2 on table1 is equal to the ID_table2 on table2.
For example, the row on table1 where the ID_table1 is 1 would have the ID_B = 14.
Can you help me on this?
Thanks in advance,
Miguel.
Using JOINs you can do as.
update table1 t1
inner join
table2 t2 on t2.ID_table2 = t1.ID_table2
set t1.ID_B = t2.ID_B
DEMO
You could try it like so:
UPDATE
table1 AS target,
(SELECT ID_table2, ID_B FROM table2) AS source
SET
target.ID_B = source.ID_B
WHERE
target.ID_TABLE2 = source.ID_table2
Database: mysql > ver 5.0
table 1: type_id (int), type
table 2: name_id, name, is_same_as = table2.name_id or NULL
table 3: id, table2.name_id, table1.type_id, value (float)
I want to sum values, and count values in table 3 where table2.name_id are same and also include the values of id where is_same_is=name_id. I want to select all data in table3 for all values in table2.
Apologize if my question is not very clear, and if it has already been answered but I am unable to find a relevant answer. Or dont exactly know what to look for.
[data]. table1
id | type
=========
1 | test1
2 | test2
[data].table2
name_id | name | is_same_as
==============================
1 | tb_1 | NULL
2 | tb_2 | 1
3 | tb_3 | NULL
4 | tb_4 | 1
[data].table3
id | name_id | type_id | value
======================================
1 | 1 | 1 | 1.5
2 | 2 | 1 | 0.5
3 | 2 | 2 | 1.0
output:
name_id| type_id|SUM(value)
=======================================================
1 | 1 |2.0 < because in table2, is_same_as = 1
2 | 2 |1.0
I think the following does what you want:
select coalesce(t2.is_same_as, t2.name_id) as name_id, t3.type_id, sum(value)
from table_3 t3 join
table_2 t2
on t3.name_id = t2.name_id
group by coalesce(t2.is_same_as, t2.name_id), t3.type_id
order by 1, 2
It joins the table on name_id. However, it then uses the is_same_as column, if present, or the name_id if not, for summarizing the data.
This might be what you are looking for: (I haven't tested it in MySQL, so there may be a typo)
with combined_names_tab (name_id, name_id_ref) as
(
select name_id, name_id from table2
union select t2a.name_id, t2b.name_id
from table2 t2a
join table2 t2b
on (t2a.name_id = t2b.is_same_as)
)
select cnt.name_id, t3.type_id, sum(t3.value) sum_val
from combined_names_tab cnt
join table3 t3
on ( cnt.name_id_ref = t3.name_id )
group by cnt.name_id, t3.type_id
having sum(t3.value) / count(t3.value) >= 3
Here's what the query does:
First, it creates 'combined_names_tab' which is a join of all the table2 rows that you want to GROUP BY using the "is_same_as" column to make that determination. I make sure to include the "parent" row by doing a UNION.
Second, once you have those rows above, it's a simply join to table3 with a GROUP BY and a SUM.
Note: table1 was unnecessary (I believe).
Let me know if this works!
john...
First, sorry if the title is confusing.
SQL is not my strong suit and I've been working on this for a while, my thoughts at the mmoment is something with a join, and group maybe.
Soto Example:
record | type | key1 | key2 | data1
---------------------------------------
1 | 1 | joe | smoe | 10
2 | 2 | homer | simpson | 20
3 | 1 | null | null | 30
4 | 3 | bart | simpson | 40
Where primary key is made up of id, key1, key2.
I only want rows of 'type' WHERE key1 is not null AND key2 is not null.
So since in record 3, type 1 has null keys, I therefore want all records of type 1 to not be included in the derived table.
Here's a correlated, "not exists" approach:
select *
from T as t1
where not exists (
select *
from T as t2
where t2.type = t1.type and (t2.key1 is null or t2.key2 is null)
)
And here's one that uses a non-correlated query along with grouping. Perhaps it's what you had in mind:
select *
from T as t1
where t1.type in (
select t2.type
from T as t2
group by t2.type
having count(*) = count(t2.key1) and count(*) = count(t2.key2)
)
Since I understand mysql query plans can be sensitive to these things. Here's the equivalent with a join:
select t1.*
from T as t1
inner join
(
select t2.type
from T as t2
group by t2.type
having count(*) = count(t2.key1) and count(*) = count(t2.key2)
) as goodtypes
on goodtypes.type = t1.type