How can I update a table (MyTable) from a aprticular database (DB1) by equating the said MyTable from a different database (DB2) but it has the same tablename with the one I need to update. I tried putting alias to my program but it doesn't work. Need Help
A SQL Server answer is
UPDATE t2
SET t2.Col1 = t1.Col1, t2.Col2 = t1.Col2
FROM DB1.dbo.MyTable AS t1 INNER JOIN
DB2.dbo.MyTable AS t2 ON t1.PK = t2.PK
(Obviously alter the joining condition and update column list as required)
Related
update t1
from
table1 t1,
table2 t2
set
t1.active_ind=0,
t1.row_status_cd='L'
where
t2.col1
is NULL
Getting "Column/ parameter table 1.t1 doesnt exists" error in Teradata SQL though those fields are available in t1 . can anybody help me to resolve this please?
As you only have to update table1 you don't need the t1 before the columnnames in tne SET, that is why you get the error.
but shouldn't there be a relation between table1 and table2, but as always you should test this first before using it, that wquery could have unforseen side effects
update t1
from
table1 t1,
table2 t2
set
active_ind=0,
row_status_cd='L'
where
t2.col1 is NULL
I noticed today that this query
select * from table1 table2 where column_from_table1 = ?;
works. It works the same as (same columns return)
select * from table1 where column_from_table1 = ?;
Shouldn't the former be a syntax error? What is it interpreting table2 as?
Appears it's interpreting it as renaming the table, even though table2 exists it happily allows the rename, this also works:
select * from table1 asdf where asdf.column_from_table1 = ?;
select * from table1 table2 where column_from_table1 = ?;
table2 is working as a table alias for table1. It's not being used as the name of an object in the database at all. The fact that a table named table2 exists is wholly irrelevant to this query. Usually you'd see something like this:
select t.id, t.name from table1 t where t.column_from_table1 = ?;
Some RDBMSs require the as keyword, so you'll also see this:
SELECT t.id, t.name FROM table1 AS t WHERE t.column_from_table1 = ?;
Table aliases are useful for making queries with multiple tables easier to write, especially if they have shared column names which need to be qualified. They're also essential for self-joins where a table is joined to itself.
Example of a join using aliases:
SELECT t1.Id,
t1.Name as t1_Name
t2.Name as t2_Name
FROM table1 t1
JOIN table2 t2
ON t1.id = t2.id
WHERE t1.column_from_table1 = ?;
Or, for a self-join to look for duplicate Name values, for example:
SELECT t1.Name,
t1.Id
t2.Id as Dupe_Id
FROM table1 t1
JOIN table1 t2
ON t1.Name = t2.Name
WHERE t1.Id < t2.Id;
Notice that this query is referring to table1 twice and uses the aliases of t1 and t2 to differentiate which it's referring to.
Note that a comma join, such as FROM table1, table2 WHERE table1.id = table2.id is very old syntax that should be explicitly avoided when writing queries. The older syntax is difficult to read and maintain and doesn't support outer joins except by vender-specific extensions. The newer syntax with the JOIN keyword was introduced in standard SQL in 1992. There's no reason to still be using comma joins.
I have read lots of post about how to update multiple columns but still can't find right answer.
I have one table and I would like update this table from another table.
Update table1
set (a,b,c,d,e,f,g,h,i,j,k)=(t2.a,t2.b,t2.c,t2.d,t2.e,t2.f,t2.g,t2.h,t2.i,t2.j,t2.k)
from
(
SELECT ..... with join ... where ....
) t2
where table1.id=table2.id
If I running only select statement (between brackets) then script return values but not working with update
TSQL does not support row-value constructor. Use this instead:
UPDATE table1
SET a = t2.a,
b = t2.b,
(...)
FROM
(
SELECT ..... with join ... WHERE ....
) t2
WHERE table1.id = table2.id
You don't need to use a sub-query you can also simply do the following....
Update t1
set t1.a = t2.a
,t1.b = t2.b
,t1.c = t2.c
,t1.d = t2.d
.......
from table1 t1
JOIN table2 t2 ON t1.id = t2.id
WHERE .......
The above solution will work only for MSSQL.
In case of MySql you just need to first declare the tables
UPDATE
table1 t1 ,table2 t2
set
t1.field=t2.field
where
t1.id=t2.id;
In my case this worked..!!
The UPDATE SET commands implicitly apply on the table specified by , and it is not possible to specify the table on the SET operation.
Edit: Specify only the column name you want to update, do not mention the table.
I have this SQL...
UPDATE table1 t1
SET (t1.wert) =
(select t2.bezeichnung from table2 t2
where t1.id = t2.cpbezeichnung)
where t1.id = t2.cpbezeichnung
... which I cant run because it says me that it doesnt know t2.cpbezeichnung in line #5.
How can I fix it?
Table with alias t2 is not defined for UPDATE query, so it's clearly not known at line 5. Table t2 is defined only inside subquery on lines 3 and 4.
What exactly are you trying to achieve with condition on line 5?
If do you want prevent setting NULL into t1.wert for rows where there is no appropriate record in table t2, then you need to replace condition on line 5
UPDATE table1 t1
SET (t1.wert) =
(select t2.bezeichnung from table2 t2 where t1.id = t2.cpbezeichnung)
where t1.id IN (SELECT t2.cpbezeichnung from table2)
This will set values in t1.wert only for records where t1.id exists in t2.cpbezeichnung.
The t2 alias (along with table2) is only visible in the subquery. My guess is that you want
UPDATE table1 t1
SET t1.wert = (select t2.bezeichnung
from table2 t2
where t1.id = t2.cpbezeichnung)
where exists (select 1
from table2 t2
where t1.id = t2.cpbezeichnung)
which updates every row where there is a match between the two tables. If that's not what you want, posting a test case would be helpful.
When using correlated subqueries you cannot use an alias from the inner query in the outer query.
The outer query knows nothing about the inner query except its results.
Ref
You will have to use a Inner join on the two tables.
Something like
UPDATE table1 t1 INNERJOIN table t2 ON your_table_condition SET t1.wert = (select t2.bezeichnung from t2 where t1.id = t2.cpbezeichnung) where t1.id = t2.cpbezeichnung
This is a common SQL query for me:
update table1 set col1 = (select col1 from table2 where table1.ID = table2.ID)
where exists (select 1 from table2 where table1.ID = table2.ID)
Is there any way to avoid having two nearly identical subqueries? This query is an obvious simplification but performance suffers and query is needlessly messy to read.
Unfortunately Informix don't support the FROM clause at UPDATE statement.
The way to workaround and you will get better results (performance) is change the UPDATE to MERGE statement.
This will work only if your database is version 11.50 or above
MERGE INTO table1 as t1
USING table2 as t2
ON t1.ID = t2.ID
WHEN MATCHED THEN UPDATE set (t1.col1, t1.col2) = (t2.col1, t2.col2);
Check IBM Informix manual for more information
Update with inner join can be used to avoid subqueries
something like this:
update t1
set col1 = t2.col1
from table1 t1
inner join table2 t2
on t1.ID = t2.ID
try this:
update table1 set col1 = (select col1 as newcol from table2 where table1.ID = table2.ID)
where exists (newcol)