I'm very rusty on my SQL, and I have to work on a query that looks something like the following:
select * from (
-- whole bunch of code here
where
-- more bits and pieces
connect by prior x = y
start with z = 'VALUE'
I want to run this query on a whole set of values, resulting from using another select statement. I'm looking for something with similar semantics to:
start with z in (select * from ...)
I'm using an Oracle SQL databse here. There are so many varieties of SQL I find it hard to get something useful from a search, I wouldn't have thought the solution is all that complicated (?). The final query does not have to be necessarily efficient, it will be run only once.
Related
I have a database with MANY out-of-date file locations. The difference between the out-of-date file locations and the correct locations is simply the left-side of the address. So, I am attempting to take the left-side off and replace it with the correct string. But, I can't get there because my query is altering the right-side of the address.
This query is made using "vfpoledb."
SELECT RIGHT(LINK,LEN(LINK)-8) ,LEN(LINK)-8,RIGHT(LINK,77),LINK
FROM LINKSTORE
WHERE DOCLBL = "V46145002A"
This query returns the following:
EXP1:
\SHARES\DATA\QMS\QMS DATA\TRACKING FILES\REMOTEENTRIES\V46145 216447
EXP2:
77
EXP3:
\SHARES\DATA\QMS\QMS DATA\TRACKING FILES\REMOTEENTRIES\V46145 216447-002A.PDF
LINK:
\\SERVER\SHARES\DATA\QMS\QMS DATA\TRACKING FILES\REMOTEENTRIES\V46145 216447-002A.PDF
I don't understand why EXP1 and EXP3 are giving different results. EXP3 is what I'm looking for EXP1 to return. If I could get that, I could append the correct left-hand-side and create an update query to fix everything.
Edit:
Even when changing the query to:
SELECT RIGHT(LINK,LEN(LINK)) ,LEN(LINK)-8,RIGHT(LINK,77),LINK
FROM LINKSTORE
WHERE DOCLBL = "V46145002A"
The link still cuts off at the same point, which is odd because expression_3 which still uses Right(), but manually provides the length instead of using Len() does not do this.
Furthermore, it seems that when I run the query to include all results:
SELECT RIGHT(LINK,LEN(LINK)) ,LEN(LINK)-8,RIGHT(LINK,77),LINK
FROM LINKSTORE
WHERE 1=1
All values returned by Exp1 are equal in length even though Exp2 and Link are different in size.
So back to the problem, how can I run a query to replace the left-side with the correct server if I can't separate them out?
OK this is tricky, I did some Foxpro 20 years ago but don't have it to hand.
Your SELECT statement looks OK to me. In the comments under the question Thomas G created this DbFiddle which shows that in a 'normal' dbms, your SELECT statement gives the result you are expecting: https://dbfiddle.uk/?rdbms=sqlserver_2017&fiddle=37047d2b7efb91aaa029fa0fb98eea24
So the problem must be something FoxPro/dBase specific rather than a problem with your SELECT statement.
Reading up I see people say that with FoxPro always use ALLTRIM() when using RIGHT() or LEN() on table fields because the data gets returned padded with spaces. I don't see how that would cause the exact bug you're seeing but you could try this maybe:
SELECT RIGHT(ALLTRIM(LINK),LEN(ALLTRIM(LINK))-8) ,LEN(ALLTRIM(LINK))-8,RIGHT(ALLTRIM(LINK),77),ALLTRIM(LINK)
FROM LINKSTORE
WHERE DOCLBL = "V46145002A"
edit: OK I got a better idea - are there other rows in your result set?
According to this: https://www.tek-tips.com/viewthread.cfm?qid=1706948 ... when you do SELECT (expr) in FoxPro whatever the length of the expr in the first row becomes that max length for that 'field' and so all subsequent rows get truncated to that length. Makes sense in a crazy 1970s sort of way.
So perhaps you have a row of data above the one we are talking about which comes out at 68 chars long and so every subsequent value gets truncated to that length.
The way around it is to pad your expression results with CAST or PADR:
SELECT PADR(RIGHT(ALLTRIM(LINK),LEN(ALLTRIM(LINK))-8),100),LEN(ALLTRIM(LINK))-8,PADR(RIGHT(ALLTRIM(LINK),77),100),LINK
FROM LINKSTORE
WHERE DOCLBL = "V46145002A"
Or same without the ALLTRIM()
SELECT PADR(RIGHT(LINK,LEN(LINK)-8),100),LEN(LINK)-8,PADR(RIGHT(LINK,77),100),LINK
FROM LINKSTORE
WHERE DOCLBL = "V46145002A"
I'm having some trouble understanding WHY a select statement isn't working in a query I'm making.
I've got the SELECT and FROM lines functioning. With just those, ALL results from my selected table are displayed - 517 or so
What I want to do is display results based on a pattern using LIKE - What I have so far
SELECT *
FROM Tbl_ServiceRequestMatrix
WHERE Tbl_ServiceRequestMatrix.[Application/Form] LIKE 'P%';
This returns 0 results - despite the fact that the column selected DOES have entries that start with 'P'
I also tried utilising brackets, see if that was the issue - still displays 0 results:
SELECT *
FROM Tbl_ServiceRequestMatrix
WHERE ((Tbl_ServiceRequestMatrix.[Application/Form])='p%');
Can any one help me understand why my WHERE ** LIKE statement is causing 0 results to be displayed?
The wildcard character in MS Access is (by default) * instead of %:
WHERE Tbl_ServiceRequestMatrix.[Application/Form] LIKE "P*"
LIKE Statement has different parameters in different sql languages.
In MS Access you need * Instead of % in LIKE Statement.
In many languages, one can use inline lists of values, with some form of code similar to this:
for x in [1,7,8,12,14,56,123]:
print x # Or whatever else you fancy doing
Working with SQL for the last year or so, I've found out that even though using such an array in WHERE is not a problem...
select *
from foo
where someColumn in (1,7,8,12,14,56,123) and someThingElse...
...I have not found an equivalent form to GET data from an inline array:
-- This is not working
select *
from (1,7,8,12,14,56,123)
where somethingElse ...
Searching for solutions, I have only found people suggesting a union soup:
select *
from (SELECT 1 UNION SELECT 1 UNION SELECT 7 UNION ...)
where somethingElse ...
...which is arguably, ugly and verbose.
I can quickly generate the UNION soup from the list with a couple of keystrokes in my editor (VIM) and then paste it back to my DB prompt - but I am wondering whether I am missing some other method to accomplish this.
Also, if there's no standard way to do it, I would still be interested in DB-engine-specific solutions (Oracle, PostgreSQL, etc)
Thanks in advance for any pointers.
Row/Table value constructors can sometimes be used as a shortish hand, for example in MSSQL:
select * from (values (1),(7),(8),(12)) as T (f)
The syntax is more complex by necessity than for a simple array-like list passed to in () because it must be able to describe a multi-dimensional set of data:
select * from (values (1, 'a'),(7, 'b'),(8, 'c'),(12, 'd')) as T (f, n)
Of course, when you find the requirement to list literal values its often a good idea to stick them in a table and query for them.
I have some sample data like:
|H.RISK|NOTE|NORMAL|
The | are actually in the data, it's a String.
I am using Access, and am trying to exclude records that contain RISK in the String.
Sample query:
SELECT * FROM someTable WHERE (UCase(someTable.Field) NOT LIKE '*RISK*') AND (UCase(someTable.Field) NOT LIKE '*Blah*') AND someTable.SomeOtherField <> 4;
The problem is, the query is returning the above sample record, even though it does contain the string RISK.
I've tried the same query but switched to OR instead of AND but get the same results.
How can I properly structure this query to exclude records which contain certain strings?
Seeing that it appears you are running using the SQL syntax, try with the correct wild card.
SELECT * FROM someTable WHERE (someTable.Field NOT LIKE '%RISK%') AND (someTable.Field NOT LIKE '%Blah%') AND someTable.SomeOtherField <> 4;
Given this linq query against an EF data context:
var customers = data.Customers.Where(c => c.EmailDomain.StartsWith(term))
You’d expect it to produce SQL like this, right?
SELECT {cols} FROM Customers WHERE EmailDomain LIKE #term+’%’
Well, actually, it does something like this:
SELECT {cols} FROM Customer WHERE ((CAST(CHARINDEX(#term, EmailDomain) AS int)) = 1)
Do you know why?
Also, replacing the Where selector to:
c => c.EmailDomain.Substring(0, term.Length) == term
it runs 10 times faster but still produces some pretty yucky SQL.
NOTE: Linq to SQL correctly translates StartsWith into Like {term}%, and nHibernate has a dedicated LikeExpression.
I don't know about MS SQL server but on SQL server compact LIKE 'foo%' is thousands time faster than CHARINDEX, if you have INDEX on seach column. And now I'm sitting and pulling my hair out how to force it use LIKE.
http://social.msdn.microsoft.com/Forums/en-US/adodotnetentityframework/thread/1b835b94-7259-4284-a2a6-3d5ebda76e4b
The reason is that CharIndex is a lot faster and cleaner for SQL to perform than LIKE. The reason is, that you can have some crazy "LIKE" clauses. Example:
SELECT * FROM Customer WHERE EmailDomain LIKE 'abc%de%sss%'
But, the "CHARINDEX" function (which is basically "IndexOf") ONLY handles finding the first instance of a set of characters... no wildcards are allowed.
So, there's your answer :)
EDIT: I just wanted to add that I encourage people to use CHARINDEX in their SQL queries for things that they didn't need "LIKE" for. It is important to note though that in SQL Server 2000... a "Text" field can use the LIKE method, but not CHARINDEX.
Performance seems to be about equal between LIKE and CHARINDEX, so that should not be the reason. See here or here for some discussion. Also the CAST is very weird because CHARINDEX returns an int.
charindex returns the location of the first term within the second term.
sql starts with 1 as the first location (0 = not found)
http://msdn.microsoft.com/en-us/library/ms186323.aspx
i don't know why it uses that syntax but that's how it works
I agree that it is no faster, I was retrieving tens of thousands of rows from our database with the letter i the name. I did find however that you need to use > rather than = ... so use
{cols} FROM Customer WHERE ((CAST(CHARINDEX(#term, EmailDomain) AS int)) > 0)
rather than
{cols} FROM Customer WHERE ((CAST(CHARINDEX(#term, EmailDomain) AS int)) = 1)
Here are my two tests ....
select * from members where surname like '%i%' --12 seconds
select * from sc4_persons where ((CAST(CHARINDEX('i', surname) AS int)) > 0) --12 seconds
select * from sc4_persons where ((CAST(CHARINDEX('i', surname) AS int)) = 1) --too few results