I had a similar question regarding selecting records based on an external table (in an unlinked table):
Access SQL FROM IN and JOINS
This time I'm trying to delete records in an internal table based on criteria in an external one.
Private Sub Command0_Click()
Dim SQLstring As String
SQLstring = "Delete * FROM Testtable1 AS tnf WHERE ([Network Location].[Testtable2].[Customers] = tnf.[Customers]) AND ([Network Location].[Testtable2].[Contract] = '2003') Or ([Network Location].[Testtable2].[Active]='N');"
DoCmd.RunSQL (SQLstring)
End Sub
Its telling me that " is not a valid name and to check if theres invalid characters or punctuation or if its too long. I cant find anything that talks about SQL lengths but i'm pretty sure this isn't too long.
Is there something I'm missing about my SQl statement I've gone through it over and over and I'm not seeing an issue.
Should the WHERE clause have an Exists (Select) clause?
Am I missing something?
Since a delete query can only delete records from one table at a time, only one dataset can be referenced in the from clause. With your current query, you would need to reference testtable2 within the from clause, which would result in an invalid delete query.
As such, you'll instead need to use where exists with a subquery, e.g.:
delete from testtable1 as t1
where exists
(
select 1 from [Network Location].[Testtable2] t2
where t2.customers = t1.customers and (t2.contract = '2003' or t2.active = 'N')
)
I've also surrounded the or expression with parentheses, as I assume that it is the desired logic to delete records with a matching customers record and either of the other two conditions, rather than deleting any record for which t2.active = 'N' (since and has operator precedence over or).
Related
So perhaps the title is a little confusing. If you can suggest better wording for that please let me know and i'll update.
Here's the issue. I've got a table with many thousands of rows and i need to update a few thousand of those many to store latest email data.
For example:
OldEmail#1.com => NewEmail#1.com
OldEmail#2.com => NewEmail#2.com
I've got a list of old emails ('OldEmail#1.com','OldEmail#2.com') and a list of the new ('NewEmail#1.com','NewEmail#2.com'). The HOPE was was to sort of do it simply with something like
UPDATE Table
SET Email = ('NewEmail#1.com','NewEmail#2.com')
WHERE Email = ('OldEmail#1.com','OldEmail#2.com')
I hope that makes sense. Any questions just ask. Thanks!
You could use a case expression:
update mytable
set email = case email
when 'OldEmail#1.com' then 'NewEmail#1.com'
when 'OldEmail#2.com' then 'NewEmail#2.com'
end
where email in ('OldEmail#1.com','OldEmail#2.com')
Or better yet, if you have a large list of values, you might create a table to store them (like myref(old_email, new_email)) and join it in your update query, like so:
update t
set t.email = r.new_email
from mytable t
inner join myref r on r.old_email = t.email
The actual syntax for update/join does vary accross databases - the above SQL Server syntax.
With accuracy to the syntax in particular DBMS:
WITH cte AS (SELECT 'NewEmail#1.com' newvalue, 'OldEmail#1.com' oldvalue
UNION ALL
SELECT 'NewEmail#2.com', 'OldEmail#2.com')
UPDATE table
SET table.email = cte.newvalue
FROM cte
WHERE table.email = cte.oldvalue
or, if CTE is not available,
UPDATE table
SET table.email = cte.newvalue
FROM (SELECT 'NewEmail#1.com' newvalue, 'OldEmail#1.com' oldvalue
UNION ALL
SELECT 'NewEmail#2.com', 'OldEmail#2.com') cte
WHERE table.email = cte.oldvalue
Consider prepared statement for rows update in large batches.
Basically it works as following :
database complies a query pattern you provide the first time, keep the compiled result for current connection (depends on implementation).
then you updates all the rows, by sending shortened label of the prepared function with different parameters in SQL syntax, instead of sending entire UPDATE statement several times for several updates
the database parse the shortened label of the prepared function , which is linked to the pre-compiled result, then perform the updates.
next time when you perform row updates, the database may still use the pre-compiled result and quickly complete the operations (so the first step above can be skipped).
Here is PostgreSQL example of prepare statement, many of SQL databases (e.g. MariaDB,MySQL, Oracle) also support it.
I have two tables related to each other. The first table has one or more number of the same attribute on the latter table. (there is a one-to-many relationship) thus the rows on the latter table includes basically the following columns: (PK, FK, attribute). Some rows of the first table does not have an attribute and are not recorded in the latter table.
I would like to list all the rows in the first table with an extra column for the attribute from the latter table. when I use inner join or where clause I cannot list the results that have no attribute. However what I want to do is to list all the rows from the first table, and if there is no attribute for it I want to make the extra column null, and if it has more than one attribute I want to concatenate them in that single column.
I am aware that I am not sharing any code here and I am asking the question in an abstract way because first I need to know which tool to use and in what way. I tried joins and sub-queries with select statement as well as methods such as ISNULL but I was not sure what I was doing and it did not work for me.
PS: I am new to the site as you can observe. Thus if you think this is not a proper way of asking questions and if you suggest removing this question off the forum I will no question asked.
SELECT TableA.*, TableB.Attribute
FROM TableA LEFT JOIN TableB ON TableA.PK = TableB.FK
Edit: I just read the original question more fully and realised that this is not quite what you're after. This will give you the NULL value you wanted if there is no related data in TableB, however you will need to write a function if you want multiple related values in TableB concatenated into the one row for a given TableA record. Create a new module and in here add the following function. I am assuming here that your PK and FK columns are Long Integer and the Attribute values are String. I am also assuming that you're working in MS-Access.
Public Function ListAttributes(lngPK As Long) As String
Dim rsAttributes As DAO.Recordset
Dim strResult as String
Set rsAttributes = CurrentDB.OpenRecordset("SELECT Attribute FROM TableB WHERE FK = " & lngPK)
Do While Not rsAttributes.EOF
strResult = strResult & ", " & rsAttributes!Attribute
rsAttributes.MoveNext
Loop
If strResult <> "" Then
strResult = Mid(strResult, 3)
End If
ListAttributes = strResult
Set rsAttributes = Nothing
End Function
Your query then becomes
SELECT *, ListAttributes(PK) FROM TableA
Note that you will now get an empty string instead of NULL for rows in TableA that have no corresponding rows in TableB, but you can always use an IIf function call to fix this if necessary.
I need to create a query for updating a column in a table with values taken from another table and matching a field.
These are the 2 tables:
tblMain
ID Autonumbering
Key Text
Stat1 Integer
tblStat1
ID Autonumbering
Key Text
Freq Integer
I want to UPDATE the tblMain.Stat1 column with tblStat1.Freq value on each record in which tblMain.Key = tblStat1.Key.
I tried this syntax (found somewhere as an example)
UPDATE tblMain
SET tblMain.Stat1 = tblStat1.Freq
WHERE tblMain.Key = tblStat1.Key;
This doesn't work and returns an error on the 2nd row.
After some trials I found that the correct syntax (built with the Access query generator) is this:
UPDATE (tblMaibn INNER JOIN tblStat1 ON tblMain.Key = tblStat1.Key)
SET tblMain.Stat1 = tblStat1.Freq;
In this 2nd syntax, there is no trace of the WHERE condition.
Can someone help me to understand what's wrong with the 1st syntax.
Since I'm building a new table (the join), how can it work on tblMain?
As I said, I found the wrong syntax as an example of UPDATE statement.
Thank you in advance.
Bye,
Ivano
What is happening in your first query on the 2nd row, is that Access isn't aware of what tblStat1 represents in your query.
The reason your 2nd query is working is because it uses an inner join on the relevant key. In order for SQL to be aware of what record in tblMain relates to which record in tblStat1, you need to use a join.
You can see in the generated code that it is updating your desired table, but joining onto the second table. The where condition is redundant as you're updating every record.
In 1st syntax, you can change:
UPDATE tblMain
SET tblMain.Stat1 = (SELECT Freq
FROM tblStat1
WHERE tblMain.Key = tblStat1.Key)
This bit within a stored proc is apparently valid sql:
DELETE TOP (#MaxRecords)
FROM Table
FROM Table B
INNER JOIN Table2 R ON B.fk = R.pk
WHERE R.Value < #DecVariable;
How can two FROM statements be put together and yet still be valid?
First of all TOP in delete syntax indicates that it is SQL Server.
It is perfect valid query, see DELETE:
FROM
An optional keyword that can be used between the DELETE keyword and the target table_or_view_name, or rowset_function_limited.
FROM table_source
Specifies an additional FROM clause. This Transact-SQL extension to DELETE allows specifying data from and deleting the
corresponding rows from the table in the first FROM clause.
This extension, specifying a join, can be used instead of a subquery in the WHERE clause to identify rows to be removed.
DELETE:
Object:
I have written this query:
UPDATE tbl_stock1 SET
tbl_stock1.weight1 = (
select (b.weight1 - c.weight_in_gram) as temp
from
tbl_stock1 as b,
tbl_sales_item as c
where
b.item_submodel_id = c.item_submodel_id
and b.item_submodel_id = tbl_stock1.item_submodel_id
and b.status <> 'D'
and c.status <> 'D'
),
tbl_stock1.qty1 = (
select (b.qty1 - c.qty) as temp1
from
tbl_stock1 as b,
tbl_sales_item as c
where
b.item_submodel_id = c.item_submodel_id
and b.item_submodel_id = tbl_stock1.item_submodel_id
and b.status <> 'D'
and c.status <> 'D'
)
WHERE
tbl_stock1.item_submodel_id = 'ISUBM/1'
and tbl_stock1.status <> 'D';
I got this error message:
Operation must use an updatable query. (Error 3073) Microsoft Access
But if I run the same query in SQL Server it will be executed.
Thanks,
dinesh
I'm quite sure the JET DB Engine treats any query with a subquery as non-updateable. This is most likely the reason for the error and, thus, you'll need to rework the logic and avoid the subqueries.
As a test, you might also try to remove the calculation (the subtraction) being performed in each of the two subqueries. This calculation may not be playing nicely with the update as well.
Consider this very simple UPDATE statement using Northwind:
UPDATE Categories
SET Description = (
SELECT DISTINCT 'Anything'
FROM Employees
);
It fails with the error 'Operation must use an updateable query'.
The Access database engine simple does not support the SQL-92 syntax using a scalar subquery in the SET clause.
The Access database engine has its own proprietary UPDATE..JOIN..SET syntax but is unsafe because, unlike a scalar subquery, it doesn’t require values to be unambiguous. If values are ambiguous then the engine silent 'picks' one arbitrarily and it is hard (if not impossible) to predict which one will be applied even if you were aware of the problem.
For example, consider the existing Categories table in Northwind and the following daft (non-)table as a target for an update (daft but simple to demonstrate the problem clearly):
CREATE TABLE BadCategories
(
CategoryID INTEGER NOT NULL,
CategoryName NVARCHAR(15) NOT NULL
)
;
INSERT INTO BadCategories (CategoryID, CategoryName)
VALUES (1, 'This one...?')
;
INSERT INTO BadCategories (CategoryID, CategoryName)
VALUES (1, '...or this one?')
;
Now for the UPDATE:
UPDATE Categories
INNER JOIN (
SELECT T1.CategoryID, T1.CategoryName
FROM Categories AS T1
UNION ALL
SELECT 9 - T2.CategoryID, T2.CategoryName
FROM Categories AS T2
) AS DT1
ON DT1.CategoryID = Categories.CategoryID
SET Categories.CategoryName = DT1.CategoryName;
When I run this I'm told that two rows have been updated, funny because there's only one matching row in the Categories table. The result is that the Categories table with CategoryID now has the '...or this one?' value. I suspect it has been a race to see which value gets written to the table last.
The SQL-92 scalar subquery is verbose when there are multiple clauses in the SET and/or the WHERE clause matches the SET's clauses but at least it eliminates ambiguity (plus a decent optimizer should be able to detects that the subqueries are close matches). The SQL-99 Standard introduced MERGE which can be used to eliminate the aforementioned repetition but needless to say Access doesn't support that either.
The Access database engine's lack of support for the SQL-92 scalar subquery syntax is for me its worst 'design feature' (read 'bug').
Also note the Access database engine's proprietary UPDATE..JOIN..SET syntax cannot anyhow be used with set functions ('totals queries' in Access-speak). See Update Query Based on Totals Query Fails.
Keep in mind that if you copy over a query that originally had queries or summary queries as part of the query, even though you delete those queries and only have linked tables, the query will (mistakenly) act like it still has non-updateable fields and will give you this error. You just simply re-create the query as you want it but it is an insidious little glitch.
You are updating weight1 and qty1 with values that are in turn derived from weight1 and qty1 (respectively). That's why MS-Access is choking on the update. It's probably also doing some optimisation in the background.
The way I would get around this is to dump the calculations into a temporary table, and then update the first table from the temporary table.
There is no error in the code. But the error is Thrown because of the following reason.
Please check weather you have given Read-write permission to MS-Access database file.
The Database file where it is stored (say in Folder1) is read-only..?
suppose you are stored the database (MS-Access file) in read only folder, while running your application the connection is not force-fully opened. Hence change the file permission / its containing folder permission like in C:\Program files all most all c drive files been set read-only so changing this permission solves this Problem.
In the query properties, try changing the Recordset Type to Dynaset (Inconsistent Updates)