I am having trouble with queries from multiple tables. My platform is SQL. The first two columns of each table (ID, Tag) are related to each other. I am trying to select data from table2 and table3 using the results from table1.
Table1 is used to determine the ID and Tag. The combination of ID and Tag is unique for this table. There are no null values in table1. In this example, I will search for the ID and Tag using the Top Weight and Bottom Weight. However, any number of criteria can be used to find the ID and Tag.
SELECT ID, Tag FROM table1 WHERE Top Weight = '22' AND Bottom Weight = '44'
I would like to take the ID and Tag results from table1, and use them for my table2 and table3 queries. For table2, the combination of the first two columns (ID, Tag) is unique. I would like to select Color, Shade, and Tint from this table. There can be null values for these columns. For table3, the combination of the first three columns (ID, Tag, Sequence) is unique. I would like to select Sequence, Length, and Width from this table. These columns can also have null values.
Is it possible to combine all three tables into a single query, and use the results of the first table to get the results of the second and third table? The example tables are only 14 rows, but in reality, there are tens of thousands of rows – so performance is critical (when is it not?). I look forward to your response, thanks.
This looks like a fairly straightforward outer join query:
select t1.id, t1.tag,
t2.Color, t2.Shade, t2.Tint,
t3.Sequence, t3.Length, t3.Width
from table1 t1
left join table2 t2 on t1.id = t2.id and t1.tag = t2.tag
left join table3 t3 on t1.id = t3.id and t1.tag = t3.tag
WHERE t1.[Top Weight] = '22' AND t1.[Bottom Weight] = '44'
Related
I have two tables and both contains columns Names and ID_Number.
table1 contains columns Names, ID_Number, Price_date
table2 contains columns Names, ID_Number, historical_date, comments
I am trying to do a loop such that it will start from the first value in ID_Number column in table1 and see if it matches with any value in ID_number column in table2.
If there is a match, then compare the 'Names' for the two tables for that particular ID_number. If the names does not matched, then in the comments column, enter the Name from table1 and enter the Price_date from table1 to historical_date in table2.
Don't use loops in SQL, as long as you can avoid them. SQL is a set-based language, that is not optimized for iterative processes.
From your explanation, it seems like you want an update statement with a join. This should do what you want:
update t2
set t2.comments = t1.names, t2.historical_date = t1.price_date
from table2 t2
inner join table1 t1
on t1.id_number = t2.id_number
and t1.names <> t2.names
I have two tables joined up together
I need to see if Product Code from table 1 (On the left) matches with the on on the right, based on their barcodes.. I have managed to inner join the barcodes and show only barcodes that match up. Just the prdouct code is the problem now...
Is this what you want?
select t1.*
from table1 t1
where not exists (select 1
from table2 t2
where t2.code = t1.product_code and t2.barcode = t1.barcode
);
This selects rows from table1 with no matches in table2.
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'
...
I have two tables with 3.5 million rows of data. I am creating a left join between the two to create a new view.
Code 1:
SELECT t1.c1,t1.c2,t2.c3,t2.c4
from table1 as t1
left join table2 as t2
on t1.Location=t2.Location and t1.OrderNumber=t2.OrderNumber and t1.Customer=t2.Customer
Code 2:
SELECT t1.c1,t1.c2,t2.c3,t2.c4
from table1 as t1
left join table2 as t2
on t1.OrderNumber=t2.OrderNumber
Both snippets of code give the same desired result as the Order number field in table 2 has only unique values.
Is it better to give more fields to JOIN compared to only one?
SELECT t1.c1,t1.c2,t2.c3,t2.c4
from table1 as t1
left join table2 as t2
on t1.Location = t2.Location
and t1.OrderNumber = t2.OrderNumber
and t1.Customer = t2.Customer
If OrderNumber is the PK of either table then adding additional fields will not change the results and it will not improve performance unless an index as not present on the other side.
If Order number field in table 2 has only unique values it would not change the query. If it is a PK or has a unique constraint/index then addition fields would not help unless what Table2.OrderNumber was joined to was not indexed.
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.