I am doing an autojoin on a table (lets say with table aliases current, prev, next) but am only interested in the columns of current.
Is there a way (without explicitly enumerating them) to limit the columns of the result set to that of current?
Something less complex (no metatable querying or even something that is entirely DB agnostic) than this: sql select with column name like would be fantastic. As I impose some specific constraints on my requirement (select all colums of the original/current table), my hope is that there is something easy that I am missing. In the end, I'd be happy with a Postgres specific solution as well.
Using Postgres, a statment like
SELECT current FROM ...
indeed nearly provides what I want except that everything now is merged into a single comma separated text column.
Sure this is possible:
select current.*
from some_table current
join other_table prev on prev.fid = current.id
join third_table nxt on nxt.oid = prev.id
Related
So I came upon a question where someone asked for a list of unused account numbers. The query I wrote for it works, but it is kind of hacky and relies on the existence of a table with more records than existing accounts:
WITH tmp
AS (SELECT Row_number()
OVER(
ORDER BY cusno) a
FROM custtable
fetch first 999999 rows only)
SELECT tmp.a
FROM tmp
WHERE a NOT IN (SELECT cusno
FROM custtable)
This works because customer numbers are reused and there are significantly more records than unique customer numbers. But, like I said, it feels hacky and I'd like to just generate a temporary table with 1 column and x records that are numbered 1 through x. I looked at some recursive solutions, but all of it looked way more involved than the solution I wound up using. Is there an easier way that doesn't rely on existing tables?
I think the simple answer is no. To be able to make a determination of absence, the platform needs to know the expected data set. You can either generate that as a temporary table or data set at runtime - using the method you've used (or a variation thereof) - or you can create a reference table once, and compare against it each time. I'd favour the latter - a table with a single column of integers won't put much of a dent in your disk space and it doesn't make sense to compute an identical result set over and over again.
Here's a really good article from Aaron Bertrand that deals with this very issue:
https://sqlperformance.com/2013/01/t-sql-queries/generate-a-set-1
(Edit: The queries in that article are TSQL specific, but they should be easily adaptable to DB2 - and the underlying analysis is relevant regardless of platform)
If you search all unused account number you can do it :
with MaxNumber as
(
select max(cusno) MaxID from custtable
),
RecurceNumber (id) as
(
values 1
union all
select id + 1 from RecurceNumber cross join MaxNumber
where id<=MaxID
)
select f1.* from RecurceNumber f1 exception join custtable f2 on f1.id=f2.cusno
Is there a way in Access using SQL to get the difference between 2 tables?
I'm building an audit function and I want to return all records from table1 where a value (or values) doesn't match the corresponding record in table2. Primary keys will always match between the two tables. They will always contain the exact same number of fields, field names, and types, as each other. However, the number and name of those fields cannot be determined before the query is run.
Please also note, I am looking for an Access SQL solution. I know how to solve this with VBA.
Thanks,
There are several possibilities to compare fields with known names, but there is no way in SQL to access fields without knowing their name. Mostly becase SQL doesn't consider fields to have a specific order in a table.
So the only way to accomplish what you need in pure Access-SQL would be, if there was a SQL-Command for it (kind of like the * as placeholder for all fields). But there isn't. Microsoft Access SQL Reference.
What you COULD do is create an SQL-clause on the fly in VBA. (I know, you said you didn't want to do it in VBA - but this is doing it in SQL, but using VBA to create the SQL..).
Doing everything in VBA would probably take some time, but creating an SQL on the fly is very fast and you can optimize it to the specific table. Then executing the SQL is the fastest solution you can get.
Not sure without your table structure but you can probably get that done using NOT IN operator (OR) using WHERE NOT EXISTS like
select * from table1
where some_field not in (select some_other_field from table2);
(OR)
select * from table1 t1
where not exists (select 1 from table2 where some_other_field = t1.some_field);
SELECT A.*, B.* FROM A FULL JOIN B ON (A.C = B.C) WHERE A.C IS NULL OR B.C IS NULL;
IF you have tables A and B, both with colum C, here are the records, which are present in table A but not in B.To get all the differences with a single query, a full join must be used,like above
SAS has a sum(of col1 - coln ) function which finds the sum of all the values from col1, col2, col3...coln. (ie, you don't have to list out all the column names, as long as they are numbered consecutively). This is a handy shortcut to find a sum of several (suitably named) variables.
Question - Is there a DB2/SQL equivalent of this? I have 50 columns (they are named col1, col2, col3....col50 and I need to find the sum of them.
ie:
select sum(col1, col2, col3,....,col50) AggregateSum
from foo.table
No, DB2 has no such beast, at least to my knowledge. However, you can dynamically create such a query by first querying the database metadata to extract the columns for a given table.
From memory, DB2 has a sysibm.syscolumns table which basically contains the column information that you could use to construct a query on the fly.
You would first use a query like:
select column for sysibm.syscolumns
where schema = 'foo' and tablename = 'table'
and column like 'col%'
(the column names may not match exactly but, since they're not the same on the differing variants of DB2 (DB2/z, DB2/LUW, iSeries DB2, etc) anyway, that hardly matters).
Then use the results of that query to construct your actual query:
select col1+col2+...+colN AggregateSum from foo.table
where the col1+col2+...+colN bit has been built from the previous query.
If, as you mention in a comment, you only want the eighteen "highest" columns (e.g., if columns 1 thru 100 exist, you only want 83 thru 100), you can modify the first query to do that, with something like:
select column for sysibm.syscolumns
where schema = 'foo' and tablename = 'table'
and column like 'col%'
order by column desc
fetch first 18 rows only
but, in that case, you may want to call the columns col0001, col0145 and so on, or make the sorting able to handle variable width numbers.
Although it may be easier (if you can't change the column names) to get all the columns colNNN, sort them yourself by the numeric (not string) value after the col, and throw away all but the last eighteen when constructing the second query).
Both these options will return only eighteen rows maximum.
But you may also want to think, in that case, about moving the variable data to another table, if that's possible in your situation. If you ever find yourself maintaining an array within a table, it's usually better to separate that out.
So your main table would then be something like:
main_id primary key
other_data
and your auxiliary table would be akin to:
main_id foreign key to main(main_id)
sequence_nm
other_data
primary key (main_id, sequence_num)
That would allow you to have sparse data if needed, and also to add data without having to change the schema of the main table. The query to get the latest eighteen results would be a little more complicated but still a relatively simple join of the two tables.
I have two tables that I am joining with the following query...
select *
from Partners p
inner join OrganizationMembers om on p.ParID = om.OrganizationId
where om.EmailAddress = 'my_email#address.com'
and om.deleted = 0
Which works great but some of the columns from Partners I want to be replaced with similarly named columns from OrganizationMembers. The number of columns I want to replace in the joined table are very few, shouldn't be more than 3.
It is possible to get the result I want by selectively choosing the columns I want in the resulting join like so...
select om.MemberID,
p.ParID,
p.Levelz,
p.encryptedSecureToken,
p.PartnerGroupName,
om.EmailAddress,
om.FirstName,
om.LastName
from Partners p
inner join OrganizationMembers om on p.ParID = om.OrganizationId
where om.EmailAddress = 'my_email#address.com'
and om.deleted = 0
But this creates a very long sequence of select p.a, p.b, p.c, p.d, ... etc ... which I am trying to avoid.
In summary I am trying to get several columns from the Partners table and up to 3 columns from the OrganizationMembers table without having a long column specification sequence at the beginning of the query. Is it possible or am I just dreaming?
select om.MemberID as mem
Use th AS keyword. This is called aliasing.
You are dreaming in your implementation.
Also, as a best practice, select * is something that is typically frowned upon by DBA's.
If you want to limit the results or change anything you must explicitly name the results, as a potential "stop gap you could do something like this.
SELECT p.*, om.MemberId, etc..
But this ONLY works if you want ALL columns from the first table, and then selected items.
Try this:
p.*,
om.EmailAddress,
om.FirstName,
om.LastName
You should never use * though. Always specifying the columns you actually need makes it easier to find out what happens.
But this creates a very long sequence
of select p.a, p.b, p.c, p.d, ... etc
... which I am trying to avoid.
Don't avoid it. Embrace it!
There are lots of reasons why it's best practice to explicity list the desired columns.
It's easier to do searches for where a particular column is being used.
The behavior of the query is more obvious to someone who is trying to maintain it.
Adding a column to the table won't automatically change the behavior of your query.
Removing a column from the table will break your query earlier, making bugs appear closer to the source, and easier to find and fix.
And anything that uses the query is going to have to list all the columns anyway, so there's no point being lazy about it!
I have a comparison I'd like to make more efficient in SQL.
The input field (fldInputField) is a comma separated list of "1,3,4,5"
The database has a field (fldRoleList) which contains "1,2,3,4,5,6,7,8"
So, for the first occurrence of fldInputField within fldRoleList, tell us which value it was.
Is there a way to achieve the following in MySQL or a Stored Procedure?
pseudo-code
SELECT *
FROM aTable t1
WHERE fldInputField in t1.fldRoleList
/pseudo-code
I'm guessing there might be some functions that are best suited for this type of comparison? I couldn't find anything in the search, if someone could direct me I'll delete the question... Thanks!
UPDATE: This isn't the ideal (or good) way to do things. It's inherited code and we are simply trying to put in a quick fix while we look at building in the logic to deal with this via normalized rows.. Luckily this isn't heavily used code.
I agree with #Ken White's answer that comma-delimited lists have no place in a normalized database design.
The solution would be simpler and perform better if you stored the fldRoleList as multiple rows in a dependent table:
SELECT t1.*, r1.fldRole
FROM aTable t1 JOIN aTableRoles r1 USING (aTable_id)
WHERE FIND_IN_SET(r1.fldRole, fldInputField);
(see the MySQL function FIND_IN_SET())
But that outputs multiple rows if multiple roles match the comma-separated input string. If you need to restrict the result to one row per aTable entry, with the first matching role:
SELECT t1.*, MIN(r1.fldRole) AS First_fldRole
FROM aTable t1 JOIN aTableRoles r1 USING (aTable_id)
WHERE FIND_IN_SET(r1.fldRole, fldInputField);
GROUP BY t1.aTable_id;
You have a terrible schema design, you know. Comma-delimited lists have no business in a DB.
That being said... You're looking for LIKE.
SELECT * FROM aTable t1 WHERE t.fldRoleList LIKE fldInputField + '%'
If the content might not always match at the beginning, add another percent sign before fldInputField.
SELECT * FROM aTable t1 WHERE t.fldRoleList LIKE '%' + fldInputField + '%'