I need my code to set values of a column based on two criteria: the value of a different column in the same table and a value of a column in a different table. Is there a way to use the where statement to look at criteria in different tables?
Below is pseudo code that doesn't work but captures what I am trying to do.
UPDATE Table1
SET CustomerStatus_2003 = 'New'
FROM Table1, Table2
WHERE Table1.Column1 = 'New'
AND Table2.Column1 = '2003'
AND Table1.Column2= Table2.Column2
Thanks for your help!
You should always alias your tables and use a JOIN when you are using more than one table in a statement. Here is some code that does what you are looking for
UPDATE t
SET myColumn = 'New'
FROM MyTable t
JOIN OtherTable t2 ON t.Column = t2.Column
WHERE t.SomeCondition
AND t2.SomeOtherCondition
Related
I am trying to update column from one table to another table of different database.
I searched on stack but found answers for PostgreSQL and SQLite. Those code ain't worked for me properly in SQL Server.
Say,
D1,D2 are the two different databases
T1 is the table
C1,C2,C3 are the columns in T1
I want to update like
UPDATE T1
SET D2.T1.C1 = D1.T1.C1
WHERE D2.T1.C2 = D1.T1.C2
Everything except the where clause works fine.
Here is some code I tried:
use DB2
GO
UPDATE TABLE1
SET COL1 = (SELECT COL1 FROM DB1.dbo.TABLE1)
WHERE COL2 = DB1.dbo.TABLE1.COL2
How shall I write this query?
Note: D1 and D2 are identical. Both have the exact same schema. Just the name and data are different. Both databases are on the same server.
SQL Server supports an update join syntax:
UPDATE t1
SET COL1 = t2.COL1
FROM TABLE1 D1.t1
INNER JOIN TABLE2 D2.t2
ON t1.COL2 = t2.COL2;
Actually, your current approach might work, but you should try changing it to this:
UPDATE TABLE1 D1.t1
SET COL1 = (SELECT t2.COL1 FROM TABLE2 D2.t2 WHERE T1.COL2 = T2.COL2);
You can simply use an INNER JOIN cause sql-server support Cross-Database Queries, so you can do as:
UPDATE T1
SET T1.Col1 = T2.Col1
FROM DataBase1.Schema.TableName T1 INNER JOIN DataBase2.Schema.TableName T2
ON T1.ID = T2.ID;
Please, visit and read Cross-Database Queries.
Or update tableName set column Name = (select columnName from second table where 1=1) i.e condition is either true or false optional though
I want to join 2 tables using an Inner Join on 2 columns, both are of (nvarchar, null) type. The 2 columns have the same data in them, but the join condition is failing. I think it is due to the spaces contained in the column values.
I have tried LTRIM, RTRIM also
My query:
select
T1.Name1, T2.Name2
from
Table1 T1
Inner Join
Table2 on T1.Name1 = T2.Name2
I have also tried like this:
on LTRIM(RTRIM(T1.Name1)) = LTRIM(RTRIM(T2.Name2))
My data:
Table1 Table2
------ ------
Name1(Column) Name2(Column)
----- ------
Employee Data Employee Data
Customer Data Customer Data
When I check My data in 2 tables with
select T1.Name1,len(T1.Name1)as Length1,Datalength(T1.Name1)as DataLenght1 from Table1 T1
select T2.Name2,len(T2.Name2)as Length2,Datalength(T2.Name2)as DataLenght2 from Table2 T2
The result is different Length and DataLength Values for the 2 tables,They are not same for 2 tables.
I can't change the original data in the 2 tables. How can I fix this issue.
Thank You
Joins do not have special rules for equality. The equality operator always works the same way. So if a = b then the join on a = b would work. Therefore, a <> b.
Check the contents of those fields. They will not be the same although you think they are:
select convert(varbinary(max), myCol) from T
Unicode has invisible characters (that only ever seem to cause trouble).
declare #t table (name varchar(20))
insert into #t(name)values ('Employee Data'),('Customer Data')
declare #tt table (name varchar(20))
insert into #tt(name)values ('EmployeeData'),('CustomerData')
select t.name,tt.name from #t t
INNER JOIN #tt tt
ON RTRIM(LTRIM(REPLACE(t.name,' ',''))) = RTRIM(LTRIM(REPLACE(tt.name,' ','')))
I would follow the following schema
Create a new table to store all the possible names
Add needed keys and indexes
Populate with existing names
Add columns to your existing tables to store the index of the name
Create relative foreign keys
Populate the new columns with correct indexes
Create procedure to perform an insert in new tables names only in case the value is not existing
Perform the join using the new indexes
I think my head is muddy or something. I'm trying to figure out how a t-sql update works without a join when updating one table from another. I've always used joins in the past but came across a stored proc where someone else created one without a join. This update is being used in SQL 2008R2 and it works.
Update table1
SET col1 = (SELECT TOP 1 colX FROM table2 WHERE colZ = colY),
col2 = (SELECT TOP 1 colE FROM table2 WHERE colZ = colY)
Obviously, colY is a field in table1. To get the same results in a select statement (not update), a join is required. I guess I don't understand how an update works behind the scenes but it must be doing some kind of join?
SQL Server translates those subqueries into joins. You can look at this by getting the query plan. You can write an equivalent query with UPDATE ... FROM ... JOIN syntax and observe the query plan to be essentially the same.
The sample code shown is unusual, hard to understand, redundant and inflexible. I recommend against using this style.
No it's doing a sub query, well two in this case. Be damn painful if you have another 98 col fields.
You can do something similar for select
select *,
(SELECT TOP 1 colX FROM table2 WHERE colZ = colY) as col1
From table1
A left join would simply be more efficient
Your example unless the dbms optimises it it running the subquery(ies) for each row in table.
Got to say whoever wrote it is less than competent.
These subqueries are what is called correlated subqueries. If you were to write the same query as a SELECT rather than an UPDATE it would look like this.
SELECT col1 = (SELECT TOP 1 table2.colX FROM table2 WHERE table2.colZ = table1.colY),
col2 = (SELECT TOP 1 table2.colE FROM table2 WHERE table2.colZ = table1.colY)
FROM table1
The JOIN is in the fact that you are referencing a column from an outside table on the inside of the subquery. Table1 is referenced in the UPDATE command. You can include a FROM clause but it isn't required for a setup like this.
You can use the same syntax in a SELECT with no join, but you need to alias the table if colY also exists in table2
SELECT (SELECT TOP 1 colX FROM table2 WHERE colZ = T.colY)
, (SELECT TOP 1 colE FROM table2 WHERE colZ = T.colY)
FROM table1 AS T
I only ever use this sort of thing when building up an ad hoc query just for my own infomation. If it's going to be put into any sort of permanent code I'll convert it to a join as it's easier to read and more maintainable.
I'm trying to update some rows in a table joined to another table. The left table is indexed by ID; the right table is joined on the same ID but has multiple rows per ID. My query looks like:
UPDATE t1
SET t1.modified = t2.created
FROM table1 t1
INNER JOIN table2 t2
ON t1.ID = t2.ID
Note that t1.modified and t2.created are both datetime.
As stated, t2 has several rows per ID, each with a different created value (so the primary key is t2, created). What I want to do is set the max value of t2.created=t1.modified. However, when joining, the t1.modified value gets updated in no particular order, so whichever row is updated last, that's the value that t1.modified gets. I tried using t1.modified=max(t2.created), but apparently I can't use aggregate functions in an update query, nor can I use an order clause (i.e. order the rows so that the last row updated will effectively be the latest value of t2.created) in the update query.
Any help you can provide me is much appreciated! Thanks!!
how about this? will this fit your need?
UPDATE t1
SET modified = isnull((SELECT max(t2.created)
FROM table2 t2
WHERE t2.ID = t1.ID), modified)
FROM table1 t1;
Use the isnull function to set modified to be itself if the value returned is null. that should take care of the null issue.
You could do it this way, although it may not be standard SQL. However it should work for SQL Server.
update t1
set t1.modified = (select max([created]) from t2 where t1.ID = t2.id)
I am trying to run a simple Update query on a certain set of rows in my sqlite db. It works, but it NULLs out all the other rows. Here is the query:
update table1 set col5 =(select col5 from table2 where table2.id = table1.id)
I know this is super easy, but I can't figure out what is going on. Can't I only update certain rows, and leave the rest alone?
try this:
update table1 inner join table2 on table1.id = table2.id
set table1.col5 = table2.col5
Edit:
Sorry, didn't realise it was sqlite. sqlite doesn't support joins in the update clause.
My best guess is you could do the following:
update table1 set col5 = (select col5 from table2 where table2.id = table1.id)
where id IN (SELECT id FROM table2)
You are using the same columns you are updating to relate the two tables. You should use a primary or secondary key to relate the two tables.
See this very similar question and its answer: SQL update from one Table to another based on a ID match