I have 8 tables all with equal number of columns and with a common column. I want to fetch data from all tables in a single query.
My table structure is TABLE1, TABLE2, TABLE3, ..... TABLE 8.
that have columns COLUMNA, COLUMNB... COLUMNE and a COMMON_COLUMN
I need to get data with a where clause where COMMON_COLUMN='X'
I will need all columns from all tables.
I used a query that goes like this..
SELECT TABLE1.*, TABLE2.*, TABLE3.*
FROM TABLE1 T1
LEFT JOIN TABLE2 T2 ON T1.COMMON_COLUMN = T2.COMMON_COLUMN,
LEFT JOIN TABLE3 T3 ON T1.COMMON_COLUMN = T3.COMMON_COLUMN
WHERE T1.COMMON_COLUMN='X' AND T2.COMMON_COLUMN='X' AND T3.COMMON_COLUMN='X'
The above query is not giving any results even if one of the tables do not have any rows. I do not want to use inner join because although the tables have a common column they do not depend on each other and I need data from all tables with a certain common column.
Also, the tables have unequal number of rows.
What am I doing wrong?
correct me if i am wrong - as you do not attach any sample data and desired result
but i assume that you simply need union all tables. You write in the title that tables are independent
SELECT T1.*
FROM TABLE1 T1
WHERE T1.COMMON_COLUMN='X'
UNION ALL
SELECT T2.*
FROM TABLE2 T2
WHERE T2.COMMON_COLUMN='X'
UNION ALL
SELECT T3.*
FROM TABLE3 T3
WHERE T3.COMMON_COLUMN='X'
...
Related
I want to join two tables in Access based on different wildcards for different rows.
The first, table1, contains rows with different wildcards and table2 contains the column that should be matched with the wildcards in table1.
I imagine the SQL code to look like:
SELECT *
FROM table2
LEFT JOIN table1
ON table2.subject LIKE table1.wildcard
The tables look like this: https://imgur.com/a/O9OPAL6
The third pictures shows the result that I want.
How do I execute the join or is there an alternative?
I don't think MySQL support non-equality conditions for JOINs. So, you can do this as:
SELECT * -- first get the matches
FROM table2 as t2, -- ugg, why doesn't it support CROSS JOIN
table1 as t1
WHERE t2.subject LIKE t1.wildcard
UNION ALL
SELECT * -- then get the non-matches
FROM table2 as t2 LEFT JOIN
table1 as t1
ON 1 = 0 -- always false but gets the same columns
WHERE NOT EXISTS (SELECT 1
FROM table1 as t1
WHERE t2.subject LIKE t1.wildcard
);
I am trying to write an SQL query that will return Table1, which has 10 columns. This table consists of a primary key id, 4 foreign key Id columns, and 5 other columns that I want to return but not change. The goal is to do a join to replace the foreign key Ids with their descriptions that are held in other tables.
Here is one attempt with the first FK Id:
Select * from Table1 t1
left join Table2 t2
on t1.BranchId = t2.BranchId;
This left join returns the description from table2, but does not replace it.
Here is another with the first FK Id:
Select t2.BranchName from Table1 t1
left join Table2 t2
on t1.BranchId = t2.BranchId;
This returns the name I want, but does not return table1 fully.
For the sake of an example you could pretend that OtherName3, OtherName4, OtherName5 are in tables Table3, Table4, Table5, respectively.
This may seem trivial for experienced SQL devs, but I am having a hard time figuring out the syntax.
Thanks!
I'm not sure what you mean by replace it.
I think you just need to list out all the columns you want:
Select t1.col1, t1.col2, t1.col3, . . .,
t2.name
from Table1 t1 left join
Table2 t2
on t1.BranchId = t2.BranchId;
I don't know what you mean by 'replace' but you just need to qualify what columns from which table you want. That goes for all tables you are joined to, especially if they have the same column name in multiple tables. I put junk columns in since I don't know your tables but you should get the general idea.
Select t2.BranchName, t1.BranchId, t1.Name, t1.Amount, t2.BranchLocation from Table1 t1
left join Table2 t2
on t1.BranchId = t2.BranchId;
I think this is what you are looking for:
select t1.*, t2.BranchName from Table1 t1
left join Table2 t2
on t1.BranchId = t2.BranchId;
Return Table1 fully (all columns) and only the description (BranchName) from Table2.
If using SQL Server, see all syntax options for the SELECT clause here:
https://msdn.microsoft.com/en-us/library/ms176104.aspx
I'm breaking my head here where I'm going wrong.
The following query:
SELECT SUM(table1.col1) FROM table1
returns value x.
And the following query:
SELECT SUM(table1.col1) FROM table2 RIGHT OUTER JOIN table1 ON table2.ID = table1.ID
returns value y. (I need the Join for the other data of table2). Why is the 2nd example returning a different value than in the first?
Make life easier on yourself, your colleagues that will support your code, and your clients by temporarily ignoring the existence of RIGHT OUTER JOIN. Use Table1 as the "from table" instead of table2.
Then, If aggregating, you will often find it necessary to do this BEFORE joining, so that the numbers are accurate. e.g.
SELECT T1.SUMCOL1
FROM (
SELECT id, SUM(col1) as SUMCOL1 FROM Table1 GROUP BY id
) T1
LEFT OUTER JOIN table2 T2 on T1.id = T2.ID
Obvious answer is because table2 is many to table1's one. That is, there are multiple rows in table2 for one id in table1. You may also be eliminating rows from table1 if the id isn't present in table2.
Compare:
SELECT COUNT(*) FROM table1
To:
SELECT COUNT(*) FROM table2 RIGHT OUTER JOIN table1 ON table2.ID = table1.ID
If you get different results, you're aggregating duplicates or eliminating rows from table1.
If you want to avoid this, you'll need to use a subquery.
I have two datasets on two seperate servers. They both pull one column of information each.
I would like to build a report showing the values of the rows that only appear in one of the datasets.
From what I have read, it seems I would like to do this on the SQL side, not the reporting side; I am not sure how to do that.
If someone could shed some light on how that is possible, I would really appreciate it.
You can use the NOT EXISTS clause to get the differences between the two tables.
SELECT
Column
FROM
DatabaseName.SchemaName.Table1
WHERE
NOT EXISTS
(
SELECT
Column
FROM
LinkedServerName.DatabaseName.SchemaName.Table2
WHERE
Table1.Column = Table2.Column --looks at equalities, and doesn't
--include them because of the
--NOT EXISTS clause
)
This will show the rows in Table1 that don't appear in Table2. You can reverse the table names to find the rows in Table2 that don't appear in Table1.
Edit: Made an edit to show what the case would be in the event of linked servers. Also, if you wanted to see all of the rows that are not shared in both tables at the same time, you can try something as in the below.
SELECT
Column, 'Table1' TableName
FROM
DatabaseName.SchemaName.Table1
WHERE
NOT EXISTS
(
SELECT
Column
FROM
LinkedServerName.DatabaseName.SchemaName.Table2
WHERE
Table1.Column = Table2.Column --looks at equalities, and doesn't
--include them because of the
--NOT EXISTS clause
)
UNION
SELECT
Column, 'Table2' TableName
FROM
LinkedServerName.DatabaseName.SchemaName.Table2
WHERE
NOT EXISTS
(
SELECT
Column
FROM
DatabaseName.SchemaName.Table1
WHERE
Table1.Column = Table2.Column
)
You can also use a left join:
select a.* from tableA a
left join tableB b
on a.PrimaryKey = b.ForeignKey
where b.ForeignKey is null
This query will return all records from tableA that do not have corresponding records in tableB.
If you want rows that appear in exactly one data set and you have a matching key on each table, then you can use a full outer join:
select *
from table1 t1 full outer join
table2 t2
on t1.key = t2.key
where t1.key is null and t2.key is not null or
t1.key is not null and t2.key is null
The where condition chooses the rows where exactly one match.
The problem with this query, though, is that you get lots of columns with nulls. One way to fix this is by going through the columns one by one in the SELECT clause.
select coalesce(t1.key, t2.key) as key, . . .
Another way to solve this problem is to use a union with a window function. This version brings together all the rows and counts the number of times that key appears:
select t.*
from (select t.*, count(*) over (partition by key) as keycnt
from ((select 'Table1' as which, t.*
from table1 t
) union all
(select 'Table2' as which, t.*
from table2 t
)
) t
) t
where keycnt = 1
This has the additional column specifying which table the value comes from. It also has an extra column, keycnt, with the value 1. If you have a composite key, you would just replace with the list of columns specifying a match between the two tables.
I am a little confused as to how to approach this SQL query.
I have two tables (equal number of records), and I would like to return a column with which is the division between the two.
In other words, here is my not-working-correctly query:
SELECT( (SELECT v FROM Table1) / (SELECT DotProduct FROM Table2) );
How would I do this? All I want it a column where each row equals the same row in Table1 divided by the same row in Table2. The resulting table should have the same number of rows, but I am getting something with a lot more rows than the original two tables.
I am at a complete loss. Any advice?
It sounds like you have some kind of key between the two tables. You need an Inner Join:
select t1.v / t2.DotProduct
from Table1 as t1
inner join Table2 as t2
on t1.ForeignKey = t2.PrimaryKey
Should work. Just make sure you watch out for division by zero errors.
You didn't specify the full table structure so I will assume a common ID column to link rows in the tables.
SELECT table1.v/table2.DotProduct
FROM Table1 INNER JOIN Table2
ON (Table1.ID=Table2.ID)
You need to do a JOIN on the tables and divide the columns you want.
SELECT (Table1.v / Table2.DotProduct) FROM Table1 JOIN Table2 ON something
You need to substitue something to tell SQL how to match up the rows:
Something like: Table1.id = Table2.id
In case your fileds are both integers you need to do this to avoid integer math:
select t1.v / (t2.DotProduct*1.00)
from Table1 as t1
inner join Table2 as t2
on t1.ForeignKey = t2.PrimaryKey
If you have multiple values in table2 relating to values in table1 you need to specify which to use -here I chose the largest one.
select t1.v / (max(t2.DotProduct)*1.00)
from Table1 as t1
inner join Table2 as t2
on t1.ForeignKey = t2.PrimaryKey
Group By t1.v