How would I go about writing a query in MySQL on 3 different tables? Here's what I have so far:
SELECT distinct cool_id, example, table1.name
FROM tardis
INNER JOIN table1
ON table1.unique_id = table2.unique_id
AND table1.unique_id='12345'
AND table2.status='active'
Now let's say that there is a column called 'planets' that exists in a 3rd table. How would I add that to this query to select 'planets' in addition to matching the other conditions in my current query? Also, please advise if an INNER JOIN is not the best choice for this.
Just add another INNER JOIN clause:
SELECT columns
FROM table1
INNER JOIN table2 ON table1.col1 = table2.col2
INNER JOIN table3 ON table1.somecol = table3.othercol
The ON condition in the second join can refer to columns from table1, table2, or both.
Related
SELECT Table1.Filter, Table1.Condition, Combined.Data FROM Table1
LEFT JOIN
(SELECT Key, Data FROM IF(Table1.Filter, Table2, Table3))) AS Combined
ON Table1.Condition = Combined.Key
I want to create a MySQL View that shows all columns of Table1, and a column from either Table2 or Table3 depending on the field on Table1.Filter.
One simple solution is to LEFT JOIN both Table2 and Table3, with NULL on the column that is not applicable. Is there a way to avoid creating 2 columns?
I cannot UNION Table2 and Table3 as they might contain the same Key.
The following should do what you want:
SELECT t1.Filter, t1.Condition,
COALESCE(t2.Data, t3.Data) as Data
FROM Table1 t1 LEFT JOIN
Table2 t2
ON t1.Filter AND t2.Key = t1.Condition LEFT JOIN
Table3 t3
ON (NOT t1.Filter) AND t3.key = t1.condition;
You cannot have conditionals choosing tables in the FROM. But, you can have conditions in the ON conditions.
So here is the thing, I have two tables:
table1 has columns intUsersID, varUsersName
table2 has columns intCouriers, intResponsible
intCouriers (have some numbers of intUsersID that are Couriers), and intResponsible (have some numbers of intUsersID that are Responsible)
In my query I must see User Names of Couriers and of the Responsible persons
something like that:
SELECT
table1.varUsersName 'Couriers',
table1.varUsersName 'Responsible'
FROM
table1
LEFT JOIN
table2 ON table2.intCouriers = table1.intUsersID
And then I need some how to subquery or join this "table1.varUsersName 'Responsible'", to get also 'Reponsible' persons. Please help me.
Should be this
SELECT table1.varUsersName 'Couriers', table2.varUsersName 'Responsible'
FROM table1
INNER JOIN table3 on table1.intUsersID = table3.intCouriers
INNER JOIN table1 as Table2 on table2.intUsersID = table3. intResponsible
SELECT Couriers.varUsersName as "Couriers",
Responsible.varUsersName as "Responsible"
FROM `table2` t2
LEFT JOIN table1 Couriers on Couriers.intUsersID = t2.intCouriers
LEFT JOIN table1 Responsible on Responsible.intUsersID = t2.intResponsible
How to create an sql table of the selected inner join table.
I would not only like to select the inner join of the two tables, but to create the table in the DB which exactly resembles that inner join. How could I achieve this?
Given two tables table1, table2 which you wish to JOIN:
SELECT *
INTO newTable IN 'YourDatabase.mdb'
FROM table1 INNER JOIN table2
ON table1.id = table2.id
You may omit out the IN 'YourDatabase.mdb' phrase if you just want the new table to be in the same database as the one where tables table1 and table2 currently are. The example I gave above is for MySQL and you may have to change it for other flavors of SQL.
to select from only one of two joined tables:
select B.* from myTableA as A inner join myTableB as B on .....
assuming you have a table myTableC that has the same columns as myTableB then
select B.* into myTableC from myTableA as A inner join myTableB as B on .....
thank you for the timed reply.
I could achieve this using,
CREATE TABLE newTable
SELECT table1.column1, table2.column2
FROM table1 INNER JOIN table2 ON
table1.id = table2.id
This is
"CREATE TABLE...............SELECT.... statement"
Query 1:
SELECT sum(total_revenue_usd)
FROM table1 c
WHERE c.irt1_search_campaign_id IN (
SELECT assign_id
FROM table2 ga
LEFT JOIN table3 d
ON d.campaign_id = ga.assign_id
)
Query 2:
SELECT sum(total_revenue_usd)
FROM table1 c
LEFT JOIN table2 ga
ON c.irt1_search_campaign_id = ga.assign_id
LEFT JOIN table3 d
ON d.campaign_id = ga.assign_id
Query 1 gives me the correct result where as I need it in the second style without using 'in'. However Query 2 doesn't give the same result.
How can I change the first query without using 'in' ?
The reason being is that the small query is part of a much larger query, there are other conditions that won't work with 'in'
You could try something along the lines of
SELECT sum(total_revenue_usd)
FROM table1 c
JOIN
(
SELECT DISTINCT ga.assign_id
FROM table2 ga
JOIN table3 d
ON d.campaign_id = ga.assign_id
) x
ON c.irt1_search_campaign_id = x.assign_id
The queries do very different things:
The first query sums the total_revenue_usd from table1 where irt1_search_campaign_id exists in table2 as assign_id. (The outer join to table3 is absolutely unnecessary, by the way, because it doesn't change wether a table2.assign_id exists or not.) As you look for existence in table2, you can of course replace IN with EXISTS.
The second query gets you combinations of table1, table2 and table3. So, in case there are two records in table2 for an entry in table1 and three records in table3 for each of the two table2 records, you will get six records for the one table1 record. Thus you sum its total_revenue_usd sixfold. This is not what you want. Don't join table1 with the other tables.
EDIT: Here is the query using an exists clause. As mentioned, outer joining table3 doesn't alter the results.
Select sum(total_revenue_usd)
from table1 c
where exists
(
select *
from table2 ga
-- left join table3 d on d.campaign_id = ga.assign_id
where ga.assign_id = c.irt1_search_campaign_id
);
I'm sure this is straight-forward, but how do I write a query in mysql that joins two tables and then returns only those records from the first table that don't match. I want it to be something like:
Select tid from table1 inner join table2 on table2.tid = table1.tid where table1.tid != table2.tid;
but this doesn't seem to make alot of sense!
You can use a left outer join to accomplish this:
select
t1.tid
from
table1 t1
left outer join table2 t2 on
t1.tid = t2.tid
where
t2.tid is null
What this does is it takes your first table (table1), joins it with your second table (table2), and fills in null for the table2 columns in any row in table1 that doesn't match a row in table2. Then, it filters that out by selecting only the table1 rows where no match could be found.
Alternatively, you can also use not exists:
select
t1.tid
from
table1 t1
where
not exists (select 1 from table2 t2 where t2.tid = t1.tid)
This performs a left semi join, and will essentially do the same thing that the left outer join does. Depending on your indexes, one may be faster than the other, but both are viable options. MySQL has some good documentation on optimizing the joins, so you should check that out..