I have a table named tbl.Products, which has a column named articlenumber and is full of numbers like s401, s402, etc.
I generated a list with new article numbers which will replace the old ones:
s401 I00010
s402 I00020
s403 I00030
s403 I00040
...
I have a query from which I hoped that it would work out, but somehow it does nothing.
(of course I have nested the other values into the query)
SELECT REPLACE('articlenumber','s401','I00010') FROM tbl.Products
How do I get a query which replaces old values with new ones in a column like this?
Doing a replace can have problems (what if you have an articles s401 and s4010?), therefore it'll be more robust to do it like this:
Update tblProducts
SET articlenumber = 'I000010'
Where articlenumber = 's401';
If you have a number of changes to do, you can either generate a little script (for example with Excel, as TheButcher suggested), or you could import the data into a little table tblVals with the columns oldVal and newVal and then use this statement:
Update tblProducts p
SET articlenumber = (Select newVal
From tblVals
where oldVal = p.articlenumber);
This allows you to do the update in one statement which again will be more robust than running a script which may run into problems if it is really long.
A third idea would be to do the logic in constructing the new number for the old number (if such a thing exists) in SQL (or a Stored Procedure) like this:
Update tblProducts p
SET articlenumber = 'I0000' || Right(articlenumber,1) || '0'
(Of course this is totally simplified and probably not nearly sufficient for your 30k rows).
You are just selecting the newly replaced values and not doing anything with them... thats a very good idea when using replace, always select first to double check that you will get the expected result :)
The update code -
Update tbl.Products
Set articlenumber = replace(articlenumber, 's401', 'I00010')
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 feel like this should be simple but I'm relatively unskilled in SQL and I can't seem to figure it out. I'm used to wrangling data in python (pandas) or Spark (usually pyspark) and this would be a one-liner in either of those. Specifically, I'm using Snowflake SQL, but I think this is probably relevant to a lot of flavors of SQL.
Essentially I just want to trim the first character off of a specific column. More generally, what I'm trying to do is replace a column with a substring of the same column. I would even settle for creating a new column that's a substring of an existing column. I can't figure out how to do any of these things.
On obvious solution would be to create a temporary table with something like
CREATE TEMPORARY TABLE tmp_sub AS
SELECT id_col, substr(id_col, 2, 10) AS id_col_sub FROM table1
and then join it back and write a new table
CREATE TABLE table2 AS
SELECT
b.id_col_sub as id_col,
a.some_col1, a.some_col2, ...
FROM table1 a
JOIN tmp_sub b
ON a.id_col = b.id_col
My tables have roughly a billion rows though and this feels extremely inefficient. Maybe I'm wrong? Maybe this is just the right way to do it? I guess I could replace the CREATE TABLE table2 AS... to INSERT OVERWRITE INTO table1 ... and at least that wouldn't store an extra copy of the whole thing.
Any thoughts and ideas are most welcome. I come at this humbly from the perspective of someone who is baffled by a language that so many people seem to have mastery over.
I'm not sure the exact syntax/functions in Snowflake but generally speaking there's a few different ways of achieving this.
I guess the general approach that would work universally is using the SUBSTRING function that's available in any database.
Assuming you have a table called Table1 with the following data:
+-------+-----------------------------------------+
Code | Desc
+-------+-----------------------------------------+
0001 | 1First Character Will be Removed
0002 | xCharacter to be Removed
+-------+-----------------------------------------+
The SQL code to remove the first character would be:
select SUBSTRING(Desc,2,len(desc)) from Table1
Please note that the "SUBSTRING" function may vary according to different databases. In Oracle for example the function is "SUBSTR". You just need to find the Snowflake correspondent.
Another approach that would work at least in SQLServer and MySQL would be using the "RIGHT" function
select RIGHT(Desc,len(Desc) - 1) from Table1
Based on your question I assume you actually want to update the actual data within the table. In that case you can use the same function above in an update statement.
update Table1 set Desc = SUBSTRING(Desc,2,len(desc))
You didn't try this?
UPDATE tableX
SET columnY = substr(columnY, 2, 10 ) ;
-Paul-
There is no need to specify the length, as is evidenced from the following simple test harness:
SELECT $1
,SUBSTR($1, 2)
,RIGHT($1, -2)
FROM VALUES
('abcde')
,('bcd')
,('cdef')
,('defghi')
,('e')
,('fg')
,('')
;
Both expressions here - SUBSTR(<col>, 2) and RIGHT(<col>, -2) - effectively remove the first character of the <col> column value.
As for the strategy of using UPDATE versus INSERT OVERWRITE, I do not believe that there will be any difference in performance or outcome, so I might opt for the UPDATE since it is simpler. So, in conclusion, I would use:
UPDATE tableX
SET columnY = SUBSTR(columnY, 2)
;
I want to append new rows to a table-1 d:\dl based on the equality constraint lower(rdl.subdir) = lower(tr.n1), where rdl and tr would be prospective aliases for f:\rdl and f:\tr tables respectively.
I get a function name is missing ). message when running the following command in VFP9:
INSERT INTO d:\dl SELECT * FROM f:\rdl WHERE (select LOWER(subdir)FROM f:\rdl in (select LOWER(n1) FROM f:\tr))
I am using the in syntax, instead of the alias based equality statement lower(rdl.subdir) = lower(tr.n1) because I do not know where to define aliases within this command.
In general, the best way to get something like this working is to first make the query work and give you the results you want, and then use it in INSERT.
In general, in SQL commands you assign aliases by putting them after the table name, with or without the keyword AS. In this case, you don't need aliases because the ones you want are the same as the table names and that's the default.
If what you're showing is your exact code and you're running it in VFP, the first problem is that you're missing the continuation character between lines.
You're definitely doing too much work, too. Try this:
INSERT INTO d:\dl ;
SELECT * ;
FROM f:\rdl ;
JOIN f:\tr ;
ON LOWER(rdl.subdir) = LOWER(tr.n1)
I'm using SQL Server. I'm also relatively new to writing SQL... in a strong way. It's mostly self-taught, so I'm probably missing key ideas in terms of proper format.
I've a table called 'SiteResources' and a table called 'ResourceKeys'. SiteResources has an integer that corresponds to the placement of a string ('siteid') and a 'resourceid' which is an integer id that corresponds to 'resourceid' in ResourceKeys. ResourceKeys also contains a string for each key it contains ('resourcemessage'). Basically, these two tables are responsible for representing how strings are stored and displayed on a web page.
The best way to consistently update these two tables, is what? Let's say I have 5000 rows in SiteResources and 1000 rows in ResourceKeys. I could have an excel sheet, or a small program, which generates 5000 singular update statements, like:
update SiteResources set resoruceid = 0
WHERE siteid IS NULL AND resourceid IN (select resourceid
from ResourceKeys where resourcemessage LIKE 'FooBar')
I could have thousands of those singular update statements, with FooBar representing each string in the database I might want to change at once, but isn't there a cleaner way to write such a massive number of update statements? From what I understand, I should be wrapping all of my statements in begin/end/go too, just in-case of failure - which leads me to believe there is a more systematic way of writing these update statements? Is my hunch correct? Or is the way I'm going about this correct / ideal? I could change the structure of my tables, I suppose, or the structure of how I store data - that might simplify things - but let's just say I can't do that, in this instance.
As far as I understand, you just need to update everything in table SiteResources with empty parameter 'placement of a string'. If so, here is the code:
UPDATE a
SET resourceid = 0
FROM SiteResources a
WHERE EXISTS (select * from ResourceKeys b where a.resourceid = b.resourceid)
AND a.siteid IS NULL
For some specific things like 'FooBar'-rows you can add it like this:
UPDATE a
SET resourceid = 0
FROM SiteResources a
WHERE EXISTS (select * from ResourceKeys b where a.resourceid = b.resourceid and b.resourcemessage IN ('FooBar', 'FooBar2', 'FooBar3', ...))
AND a.siteid IS NULL
Let me see if I understood the question correctly. You'd like to update resourceid to 0 if the resourcemessage corresponds to a list of strings ? If so, you can build your query like this.
UPDATE r
SET resourceid = 0
FROM SiteResources r
JOIN ResourceKeys k ON r.resourceid = k.resourceid
WHERE k.resourcemessage IN ('FooBar', ...)
AND r.siteid IS NULL;
This is using an extended UPDATE syntax in transact-sql allowing you to use a JOIN in the UPDATE statement. But maybe it's not exactly what you want ? Why do you use the LIKE operator in your query, without wildcard (%) ?
With table-valued parameters, you can pass a table from your client app to the SQL batch that your app submits for execution. You can use this to pass a list of all the strings you need to update to a single UPDATE that updates all rows at once.
That way you don't have to worry about all of your concerns: the number of updates, transactional atomicitty, error handling. As a bonus, performance will be improved.
I recommend that you do a bit of research what TVPs are and how they are used.
I have created a lookup table in Access to provide the possible values for a column. Now I need to update this column with the data it had before I converted the column. I am unable to figure out a SQL Query that will work. I keep getting the error "An UPDATE or DELETE query cannot contain a multi-valued field." My research has suggested that I just need to set the value of the column but this always updates 0 records:
UPDATE [table_name] SET [column_name].Value = 55 WHERE [table_name].ID = 16;
I know this query will work if I change it to update a text column, so it is definitely a problem with just this column.
If you're adding a value to your multi-valued field, use an append query.
INSERT INTO table_name( [column_name].Value )
VALUES (55)
WHERE ID = 16;
If you want to change one particular value which exists in your multi-valued field, use an UPDATE statement. For example, to change the 55 to 56 ...
UPDATE [table_name]
SET [column_name].Value = 56
WHERE [column_name].Value = 55 And ID = 16;
See Using multivalued fields in queries for more information.
I have figured this out! It certainly was counter-intuitive! You have to use an INSERT statement to do the update.
-- Update a record with a multi-valued field that has no value
INSERT INTO [table_name] ( [[column_name].[Value] )
VALUES(55)
WHERE [table_name].ID = 16;
This confused me because I was expecting an UPDATE statement. I think it actually inserts a record into a hidden table that is used to associate multiple values with this column.
I am working with Sharepoint, I created the tables as multi-value fields, ran into the error with my INSERT INTO statement, went back to Sharepoint to change to non-multi-value fields, but that didn't fix it.
Recreated the table without using multi-value fields, and the INSERT INTO worked just fine.
do not use the .value part
UPDATE [table_name] SET [column_name] = 55 WHERE [table_name].ID = 16;
INSERT INTO Quals (cTypes.[value])
SELECT Quals_ContractTypes.ContractType
FROM Quals_ContractTypes
WHERE (Quals.ID = Quals_ContractTypes.ID_Quals);
I gotta say I didn't understand very well your problem but I saw something strange in your query. Try this:
UPDATE [table_name] SET [column_name]= 55 WHERE [table_name].ID = 16;
UPDATE:
Look at this link: it has an example
UPDATE Issues
SET Issues.AssignedTo.Value = 10
WHERE (((Issues.AssignedTo.Value)=6)
AND ((Issues.ID)=8));
NOTES
You should always include a WHERE
clause that identifies only the
records that you want to update.
Otherwise, you will update records
that you did not intend to change. An
Update query that does not contain a
WHERE clause changes every row in the
table. You can specify one value to
change.
The Multi-Valued field refers to Access databases that have tables with columns, that allow you to select multiple values, like a Combo Checkbox list.
THOSE are the only Access types that SQL cannot work with. I've tested all Access lookup possibilities, including hard-coded values, and lookup tables. They work fine, but if you have a column that has the Allow Multiple select options, you're out of luck. Even using the INSERT INTO as mentioned below, will not work as you'll get a similar but different error, about INSERTing into multi-valued fields.
As mentioned it's best to avoid using such tables outside of Access, and refer to a table specifically for your external needs. Then write a macro/vba script to update the real tables with the data from the "auxiliary" table.