I have the problem of needing to update multiple columns (2) in multiple rows (7) from a subselect query.
Here is what I have so far:
UPDATE commandtbl2 t1
SET (attr, attr2) = (
SELECT attr, attr2
FROM commandtbl3 t2
WHERE t1.cmd=t2.cmd
);
However when I let that run I get SQLCODE=-811, SQLSTATE=21000
(THE RESULT OF AN EMBEDDED SELECT STATEMENT OR A SUBSELECT IN THE SET CLAUSE OF AN UPDATE STATEMENT IS A TABLE OF MORE THAN ONE ROW, OR THE RESULT OF A SUBQUERY OF A BASIC PREDICATE IS MORE THAN ONE VALUE)
Where is my mistake? It should change the 2 columns in 3 rows and leave the others rows as they are. I can only use SQL so no Java, PHP and so on.
Since this is DB2 solutions I have found online like:
UPDATE commandtbl2 t1
SET attr = t2.attr, attr2=t2.attr2
FROM commandtbl2 t1
JOIN commandtbl3 t2
ON t1.cmd = t2.cmd ;
Or
UPDATE
commandtbl2 t1
JOIN
commandtbl3 t2 ON t1.cmd=t2.cmd
SET
t1.attr = t2.attr,
t1.attr2=t2.attr2;
don't work but throw exceptions.
Thanks for your help.
TheVagabond
I think your first version should work. But here is another idea:
UPDATE commandtbl2
SET attr = t2.attr, attr2 = t2.attr2
FROM commandtbl3 t2
WHERE commandtbl2.cmd = t2.cmd ;
The version of DB2 matters. In V10, you may need two subqueries:
UPDATE commandtbl2
SET attr = (SELECT t2.attr FROM commandtbl3 t2 WHERE commandtbl2.cmd = t2.cmd FETCH FIRST 1 ROW ONLY),
attr2 = (SELECT t2.attr2 FROM commandtbl3 t2 WHERE commandtbl2.cmd = t2.cmd FETCH FIRST 1 ROW ONLY);
Note: Normally when using FETCH FIRST 1 ROW ONLY, you would have an ORDER BY.
Use a join:
UPDATE commandtbl2 t1 JOIN commandtbl3 t2 ON t1.cmd=t2.cmd SET t1.attr=t2.attr, t1.attr2=t2.attr2;
Problem is probably as stated, you try to update one row (or multiple) with the values of more rows.
Related
I want to update a column of a table1 but I should update only records where conditions are true in another table
something like this, but I don't know how to implement this purpose in Oracle SQL
update table1
join table2 on table1.msg_id = table2.id
set table1.index = table1.index-1
where table1.index > 10 and table2.type = 'myType'
I would write this as an exists subquery in any database:
update table1 t1
set index = t1.index - 1
where table1.index > 10 and
exists (select 1
from table2
where t2.id = t1.msg_id and
t2.type = 'myType'
);
The join sort of implies that you are going to use data from table2 in the update of table1. Instead, you simply want to change a value in a row when a particular condition is met.
Oracle does not support this syntax (sigh).
For your use case, you could use a not exists condition with a correlated subquery instead:
update table1
set table1.index = table1.index - 1
where
table1.index > 10
and exists (
select 1 from table2 where table1.msg_id = table2.id and table2.type = 'mytype'
)
Note: make your live easier, do not use index for a column name. This is a reserved work in pretty much all RDBMS.
How do you write a update statement with a Sub-Select in an Oracle Environment (SQL Developer)?
Example: UPDATE table SET column = (SELECT....)
Every time I try this it gives me ORA-01427 "Sub select returns more then one row" even if there is no WHERE clause..
Based on the understanding of your question I'd suggest use Merge statement.
Merge into Table1
Using
(SELECT * from table2 where condition) Temp
On (Table1.columname condition Temp.columname)
When matched Then update Set Table1.column_name = Temp.column_name;
Table1 is the table where you want to update the records.
Table2 is the table from which you want to get the data (The sub query which you are talking about )
Using this merge statement you will be able to update n number of rows.
If you want to update multiple rows, you can either use a MERGE statement (as in #jackkds7's answer above) or you can use a filter on your subselect:
UPDATE table t1
SET column = ( SELECT column FROM table2 t2 WHERE t2.key = t1.key );
If there aren't matches in table2 for all the records in table then column will be set to NULL for the non-matches. To avoid that, add a WHERE EXISTS clause:
UPDATE table t1
SET column = ( SELECT column FROM table2 t2 WHERE t2.key = t1.key )
WHERE EXISTS ( SELECT 1 FROM table2 t2 WHERE t2.key = t1.key );
Oh and in the event that key is not unique for table2, you can aggregate (up to you to figure out which function would be best):
UPDATE table t1
SET column = ( SELECT MAX(column) FROM table2 t2 WHERE t2.key = t1.key )
WHERE EXISTS ( SELECT 1 FROM table2 t2 WHERE t2.key = t1.key );
Hope this helps.
I think it would help if you posted your actual query.
In essence, the "inner" select would be executed for each row that would be updated. This inner select query is called a correlated subquery:
UPDATE table t SET t.column = (
select ot.othercolumn from othertable ot
where ot.fk = t.id --This is the correlation part, that finds
--he right value for the row you are currently updating
)
You must ensure the subquery you use will always return just a single row and a single column for every time it runs (that is, for every row that is going to be updated). If needed, you can use MAX(), or ROWNUM to ensure you always only get 1 value
More examples:
Using Correlated Subqueries
My query is as follow:
UPDATE t1 SET t1.foreign_key = (SELECT id FROM t2 WHERE t2.col = %s )
WHERE t1.col = %s
How do I return some attributes of the updated row in the table in the same query?
Use the RETURNING clause.
The optional RETURNING clause causes UPDATE to compute and return
value(s) based on each row actually updated. Any expression using the
table's columns, and/or columns of other tables mentioned in FROM, can
be computed. The new (post-update) values of the table's columns are used.
Typically, it's smarter to use a join instead of a correlated subquery:
UPDATE t1
SET foreign_key = t2.id
FROM t2
WHERE t2.col = %s
AND t1.col = %s
RETURNING t1.*; -- or only selected columns
With your original query, if the subquery finds no row in t2, t1 is updated anyway and t1.col is set to null. Typically, you'd rather not update the row in this case, which is what my query does instead.
BTW, target columns in the SET clause cannot be table-qualified (only one table is updated anyway). The manual once more:
Do not include the table's name in the specification of a target
column — for example, UPDATE table_name SET table_name.col = 1 is invalid.
You can use the RETURNING clause:
UPDATE t1
SET t1.foreign_key = (SELECT id FROM t2 WHERE t2.col = %s )
WHERE t1.col = %s
RETURNING *;
The documentation is part of the UPDATE statement.
First, SQL is not my strength. So I need help with the following problem. I'll simplify the table contents to describe the problem.
Let's start with three tables : table1 with columns id_1 and value, table2 with columns id_2 and value, and table3 with columns id_3 and value. As you'll notice, a field value appears in all three tables, while ids have different column names. Modifying column names is not an option because they are used by Java legacy code.
I need to set table3.value using table1.value or table2.value according to the fields table1.id_1, table2.id_2 and table3.id_3.
My last attempt, which describes what I try to do, is the following:
UPDATE table3
SET value=(IF ((SELECT COUNT(\*) FROM table1 t1 WHERE t1.id_1=id_3) > 0)
SELECT value FROM table1 t1 WHERE t1.id_1=id_3
ELSE IF ((SELECT COUNT(\*) FROM table2 t2 WHERE t2.id_2=id_3)) > 0)
SELECT value FROM table2 t2 WHERE t2.id_2=id_3)
Here are some informations about the tables and the update.
This update will be included in an XML file used by Liquibase.
It must work with Oracle or SQL Server.
An id from table3.id_3 can be found at most once in table1.id_1 or in table2.id_2, but not in both tables simultaneously.
If table3.id_3 is not found in table1.id_1 nor in table2.id_2, table3.value remains null.
As you can imagine, my last attempt failed. In that case, the IF command was not recognized during the Liquibase update. If anyone has any ideas how to deal with this, I'd appreciate. Thanks in advance.
I don't know Oracle very well, but a SQL Server approach would be the following using COALESCE() and OUTER JOINs.
Update T3
Set Value = Coalesce(T1.Value, T2.Value)
From Table3 T3
Left Join Table2 T2 On T3.Id_3 = T2.Id_2
Left Join Table1 T1 On T3.Id_3 = T1.Id_1
The COALESCE() will return the first non-NULL value from the LEFT JOIN to tables 1 and 2, and if a record was not found in either, it would be set to NULL.
It is Siyual's UPDATE written with MERGE operator.
MERGE into table_1
USING (
SELECT COALESCE(t2.value, t3.value) as value, t1.id_1 as id
FROM table_1 t1, table_2 t2, table_3 t3
WHERE t2.id_2 = t3.id_3 and t1.id_1 = t2.id_2
) t on (table_1.id_1 = t.id)
WHEN MATCHED THEN
UPDATE SET table_1.value = t.value
This should work in Oracle.
In Oracle
UPDATE table3 t
SET value=COALESCE((SELECT value FROM table1 t1 WHERE t1.id_1=t.id_3),
(SELECT value FROM table2 t2 WHERE t2.id_2=t.id_3))
Given your assumption #3, you can use union all to put together tables 1 and 2 without running the risk of duplicating information (at least for the id's of interest). So a simple merge solution like the one below should work (in all DB products that implement the merge operation).
merge into table3
using (
select id_2 as id, value from table2
union all
select id_3, value from table 3
) t
on table3.id_3 = t.id
when matched
then update set table3.value = t.value;
You may want to test the various solutions and see which is most effective for your specific tables.
(Note: merge should be more efficient than the update solution using coalesce, at least when relatively few of the id's in table3 have a match in the other tables. This is because the update solution will re-insert NULL where NULL was already stored when there is no match. The merge solution avoids this unnecessary activity.)
I want to do a query to update values that I forgot to copy over in a mass insert. However I'm not sure how to phrase it.
UPDATE table
SET text_field_1 = (SELECT text_field_2
FROM other_table
WHERE id = **current row in update statement, outside parens**.id )
How do I do this? It seems like a job for recursion.
Use:
UPDATE YOUR_TABLE
SET text_field_1 = (SELECT t.text_field_2
FROM other_table t
WHERE t.id = YOUR_TABLE.id)
Warning
If there's no supporting record in other_table, text_field_1 will be set to NULL.
Explanation
In standard SQL, you can't have table aliases on the table defined for the UPDATE (or DELETE) statement, so you need to use full table name to indicate the source of the column.
It's called a correlated subquery -- the correlation is be cause of the evaluation against the table from the outer query.
Clarification
MySQL (and SQL Server) support table aliases in UPDATE and DELETE statement, in addition to JOIN syntax:
UPDATE YOUR_TABLE a
JOIN OTHER_TABLE b ON b.id = a.id
SET a.text_field_1 = b.text_field_2
...is not identical to the provided query, because only the rows that match will be updated -- those that don't match, their text_field_1 values will remain untouched. This is equivalent to the provided query:
UPDATE YOUR_TABLE a
LEFT JOIN OTHER_TABLE b ON b.id = a.id
SET a.text_field_1 = b.text_field_2
If there is one ID field:
UPDATE updtable t1
SET t1.text_field_1 = (
SELECT t2.text_field_2
FROM seltable t2
WHERE t1.ID = t2.ID
)
;
UPDATE Table1, Tabl2
SET Table1.myField = Table2.SomeField
WHERE Table1.ID = Table2.ID
Note: I have not tried it.
This will only update records where IDs match.
Try this:
UPDATE table
SET text_field_1 = (SELECT text_field_2
FROM other_table
WHERE id = table.id )