I'm using SQL Server 2016 and I have a view setup for novice end users.
To start, let's say there is a table like the following:
id number
=========
1 2
2 4
3 6
4 NULL
5 12
If a user makes a query on the view such as, select * from view1 where number <> 12, the view is setup to return NULL values as -99 using coalesce(number,-99):
Result of 'select * from view1 where number <> 12':
id number
=========
1 2
2 4
3 6
4 -99
Is there anyway to have the view return NULL instead of -99 (or whatever value), without the end user having to include ... or where is null in their query?
I understand NULLs and why it behaves like this, but for convenience I'd rather these end users not have to do this.
No.
The best you can do is fix the result so it decodes -99 as NULL:
SELECT id, CASE WHEN number = -99 THEN NULL ELSE number END AS number
FROM view1
WHERE number != 12
which I believe defeats the purpose of not exposing NULL values to the end user, or approach the data by accounting NULL as a valid data, using OR number IS NULL in that matter.
Try this:
select * from view1 where number <> 12 or number is null
Related
I want to take a value from a selected column to operate the next column. For example:
SELECT CASE
WHEN ID < 4 THEN ID
ELSE 10
END
AS MY_ID,
MY_ID + 5 AS EXTRA_ID
FROM FOO
That would output for IDs 1,2,3,4,5:
MY_ID EXTRA_ID
1 6
2 7
3 8
10 15
10 15
If I do MY_ID + 5 it will complain about MY_ID not existing (it's an alias, so it makes sense) and ID + 5 will read 1+5, 2+5, 3+5, 4+5, 5+5 instead of 1+5, 2+5, 3+5, 4+10, 5+10 when it goes through the ELSE. Is it even possible to do this? I'm doing it in SSRS - Report builder, and need to operate a result that might be set to a defualt value depending on the CASE clause.
You can repeat the same CASE expression with +5 in the end for the extra_id column
SELECT CASE
WHEN ID < 4 THEN ID
ELSE 10
END
AS MY_ID,
CASE
WHEN ID < 4 THEN ID
ELSE 10
END + 5 AS EXTRA_ID
FROM FOO
An alternative is to create the extra_id column value inside SSRS using an expression
= Fields!my_id.value + 5
you cannot reuse the calculation in the same level. Using my_id in the where clause will fail as well. Either you have to calucate it multiple times, place another select around your statement or use a with statement (CTE).
Simply wrap it with another select:
SELECT t.*,
t.my_id + 5 as extra_id
FROM(Your Query) t
Derived columns are not available in the same layer they're being created. By wrapping them with another select, you make them available (that because the inner query is being processed before the outer) .
You just need a subquery to create MY_ID before doing anything with it. By creating MY_ID in the inner query the outer query can use to define new fields.
SELECT
a.MY_ID,
a.MY_ID + 5 AS EXTRA_ID
from
(SELECT
CASE
WHEN ID < 4 THEN ID
ELSE 10
END
AS MY_ID
FROM FOO) as a
I have 2 tables I am combining and that works but I think I designed the second table wrong as I have a column for each item of what really is a multiple choice question. The query is this:
select Count(n.ID) as MemCount, u.Pay1Click, u.PayMailCC, u.PayMailCheck, u.PayPhoneACH, u.PayPhoneCC, u.PayWuFoo
from name as n inner join
UD_Demo_ORG as u on n.ID = u.ID
where n.MEMBER_TYPE like 'ORG_%' and n.CATEGORY not like '%_2' and
(u.Pay1Click = '1' or u.PayMailCC = '1' or u.PayMailCheck = '1' or u.PayPhoneACH = '1' or u.PayPhoneCC = '1' or u.PayWuFoo = '1')
group by u.Pay1Click, u.PayMailCC, u.PayMailCheck, u.PayPhoneACH, u.PayPhoneCC, u.PayWuFoo
The results come up like this:
Count Pay1Click PayMailCC PayMailCheck PayPhoneACH PayPhoneCC PayWuFoo
8 0 0 0 0 0 1
25 0 0 0 0 1 0
8 0 0 0 1 0 0
99 0 0 1 0 0 0
11 0 1 0 0 0 0
So the question is, how can I get this to 2 columns, Count and then the headers of the next 6 headers so the results look like this:
Count PaymentType
8 PayWuFoo
25 PayPhoneCC
8 PayPhoneACH
99 PayMailCheck
11 PayMailCC
Thanks.
Try this one
Select Count,
CASE WHEN Pay1Click=1 THEN 'Pay1Click'
PayMailCC=1 THEN ' PayMailCC'
PayMailCheck=1 THEN 'PayMailCheck'
PayPhoneACH=1 THEN 'PayPhoneACH'
PayPhoneCC=1 THEN 'PayPhoneCC'
PayWuFoo=1 THEN 'PayWuFoo'
END as PaymentType
FROM ......
I think indeed you made a mistake in the structure of the second table. Instead of creating a row for each multiple choice question, i would suggest transforming all those columns to a 'answer' column, so you would have the actual name of the alternative as the record in that column.
But for this, you have to change the structure of your tables, and change the way the table is populated. you should get the name of the alternative checked and put it into your table.
More on this, you could care for repetitive data in your table, so writing over and over again the same string could make your table grow larger.
if there are other things implied to the answer, other informations in the UD_Demo_ORG table, then you can normalize the table, creating a payment_dimension table or something like this, give your alternatives an ID such as
ID PaymentType OtherInfo(description, etc)...
1 PayWuFoo ...
2 PayPhoneCC ...
3 PayPhoneACH ...
4 PayMailCheck ...
5 PayMailCC ...
This is called a dimension table, and then in your records, you would have the ID of the payment type, and not the information you don't need.
So instead of a big result set, maybe you could simplify by much your query and have just
Count PaymentId
8 1
25 2
8 3
99 4
11 5
as a result set. it would make the query faster too, and if you need other information, you can then join the table and get it.
BUT if the only field you would have is the name, perhaps you could use the paymentType as the "id" in this case... just consider it. It is scalable if you separate to a dimension table.
Some references for further reading:
http://beginnersbook.com/2015/05/normalization-in-dbms/ "Normalization in DBMS"
http://searchdatamanagement.techtarget.com/answer/What-are-the-differences-between-fact-tables-and-dimension-tables-in-star-schemas "Differences between fact tables and dimensions tables"
I have a Sybase table (which I can't alter) that I am trying to get into a specific table format. The table contains three columns all which are string values, with an id (which is not unique), a "position" which is a number that represents a field name, and a field column that is the value. The table looks like:
id position field
100 0 John
100 1 Jane
100 2 25
100 3 50
101 0 Dave
101 3 30
Position 0 means "SalesRep1", Position 1 means "SR1Commission", Position 2 means "SalesRep2", and Position 3 means "SR2Commission".
I am trying to get a table that looks like following, with the Commission columns being decimals instead of strings:
id SalesRep1 SR1Commission SalesRep2 SR2Commisson
100 John 25 Jane 50
101 Dave 30 NULL NULL
I've gotten close using CASE, but I end up with only one value per row and not sure there's a way to do what I want. I also have problems with trying to get CAST included to change the commission values from strings to decimals. Here's what I have so far:
SELECT id
CASE "position" WHEN '0' THEN field END AS SalesRep1,
CASE "position" WHEN '1' THEN field END AS SalesRep2,
CASE "position" WHEN '2' THEN field END AS SR1Commission,
CASE "position" WHEN '3' THEN field END AS SR2Commission
FROM v_custom_field WHERE id = ?
This gives me the following result when querying for id 100:
id SalesRep1 SR1Commission SalesRep2 SR2Commission
100 John NULL NULL NULL
100 NULL 25 NULL NULL
100 NULL NULL Jane NULL
100 NULL NULL NULL 50
This is close, but I want to 'collapse' the rows down into one row based off of the id as well as cast the commission values to numbers. I tried adding in a CAST(field AS DECIMAL) I'm not sure if this is even the right direction to go, and was looking into PIVOT, but Sybase doesn't seem to support that.
This is known as an entity-attribute-value table. They're a pain to work with because they're one step removed from being relational data, but they're very common for user-defined fields in applications.
If you can't use PIVOT, you'll need to do something like this:
SELECT DISTINCT s.id,
f0.field AS SalesRep1,
CAST(f1.field AS DECIMAL(20,5)) AS SR1Commission,
f2.field AS SalesRep2,
CAST(f3.field AS DECIMAL(20,5)) AS SR2Commission
FROM UnnamedSalesTable s
LEFT JOIN UnnamedSalesTable f0
ON f0.id = s.id AND f0.position = 0
LEFT JOIN UnnamedSalesTable f1
ON f1.id = s.id AND f1.position = 1
LEFT JOIN UnnamedSalesTable f2
ON f2.id = s.id AND f2.position = 2
LEFT JOIN UnnamedSalesTable f3
ON f3.id = s.id AND f3.position = 3
It's not very fast because it's a ton of self-joins followed by a DISTINCT, but it does work.
Let's say I have a table called nameAge:
ID Name Age
1 X 12
2 Y 12
3 null null
4 Z 12
and when I run a query like:
select * from nameAge where Age <> 12
it returns me an empty result set while I have row with id 3 where age is different than null?
Using Sql Server 2008 R2.
Any ideas?
Edit: Possibility to be duplicate with suggested answer may be at one point but does not cover at all and it shows how to use null values when compared with null but what I wanted to ask was about the result set which includes null values
This is the intended behavior. You cannot compare NULL values using = or <>. You have to use IS NULL or IS NOT NULL.
If you want NULL values only use IS NULL:
select * from nameAge where age IS NULL
If you want NULL values with age <> 12 values, use:
select * from nameAge where age <> 12 OR age IS NULL
The expression
WHERE NULL <> 12
does not return TRUE or FALSE, but actually returns UNKNOWN. This means that the third record in your table will not be returned by your query.
As #ughai mentioned, you should use IS NULL instead to query that record:
SELECT * FROM nameAge WHERE age IS NULL
Have a look at the Microsoft SQL Server documentation for more information.
When you are dealing with NULLs you should be always careful because of 3 valued logic used in Sql Server(when a predicate can be evaluated to TRUE, FALSE or UNKNOWN). Now here is a classic select statement where many newcomers make a mistake, suggesting that the statement would return all rows where Age <> 12 including NULLs.
But if you know the easy fact that comparing NULL to any value, even to NULL itself will evaluate to UNKNOWN it is getting more clear what is going on. WHERE clause will return ONLY those rows where predicate is evaluated to TRUE. Rows where predicate evaluates to FALSE or UNKNOWN will be filtered out from resultset.
Now let's see what is going on behind the scene. You have 4 rows:
ID Name Age
1 X 12
2 Y 12
3 null null
4 Z 12
and the predicate is:
where Age <> 12
When you evaluate this predicate for each row you get:
ID Name Age Evaluation result
1 X 12 FALSE --(because 12 <> 12 is FALSE)
2 Y 12 FALSE --(because 12 <> 12 is FALSE)
3 null null UNKNOWN --(because NULL <> 12 is UNKNOWN)
4 Z 12 FALSE --(because 12 <> 12 is FALSE)
Now remember that WHERE clause will return only rows where predicate evaluates to TRUE and it is clear that you will not get any result because no row evaluates to TRUE.
I wrote the following SQL to create a column that I can use to populate check boxes in a Grid to manage user permissions.
SELECT access_b2b.access_id,
access_b2b.description,
'active'= CASE
WHEN access_group.group_id IS NOT NULL THEN 1
ELSE 0
END
FROM access_b2b
LEFT JOIN access_group
ON access_group.access_id = access_b2b.access_id
WHERE ( access_group.group_id = 10
OR access_group.group_id IS NULL )
However, it does not select all of the entries from access_b2b. The issues is with the last line:
where (access_group.group_id=10 or access_group.group_id is null)
Without it, i get duplicate entries returned with different active values. Also, I realized that this is not the proper condition, because an entry in access_group might exist for a different access_group.group_id, meaning that not all the remaining entries will be pulled in with the access_group.group_id is null.
I am trying to write my condition so that if does something along the lines of:
This is the format I was trying to follow:
Where For Each unique access_id in access_group
select the one where group_id=10
if no group_id=10
select any other one
end
end
Ultimately, the goal is to have a column returned with 1 or 0 denoting if the access_id exists for a predetermined group id.
Please note that throughout this explanation I used group_id=10 for simplification, it will be later replaced with a SqlParameter.
Any help is appreciated, thank you so much!
SAMPLE DATA (only useful columns shown to simplify data)
access_group
access_id group_id
27 1
27 11
28 1
28 11
33 1
33 3
33 11
43 11
44 1
44 10
44 11
...
access_b2b
access_id description
1 Add
2 Edit
3 Delete
4 List
5 Payments
6 Open Files
7 Order
8 Mod
...
Change the query to and it should work:
SELECT access_b2b.access_id,
access_b2b.description,
'active'= CASE
WHEN access_group.group_id IS NOT NULL THEN 1
ELSE 0
END
FROM access_b2b
LEFT JOIN access_group
ON access_group.access_id = access_b2b.access_id
AND ( access_group.group_id = 10
OR access_group.group_id IS NULL )
If you don't want the records to be filtered by the WHERE clause, move the condition in the JOIN.
The JOIN will keep the lines and populate them with NULL if the condition is not met, while the WHERE clause will filter the result set.