I use in my Project the IfExistsTable function; in order to see the existence of a table.
For this purpose I use the Select statement as follows.
MASQLComm = New SqlCommand("SELECT COUNT(*) AS [RecCount] From sys.tables WHERE name Like '%" & tName & "%'", SQLConn)
RecCount = CInt(MASQLComm.ExecuteScalar)
After that I take the number which returned in RecCount. Until now the numbers was 1 and 0
And so I was turn the numbers in True or False.
Now suddenly the returned number is 2 which I can’t understand what it means.
Count return the number of rows in the table. You should not expect it to be 0 or 1 only.
You can argue that there can't be more then one table with one name, but the problem is that your query uses like '%TableName%'. So if you have table MyTable and BestTable, and you want to check if Table exits, the result of count will be 2, although there are is no table with such name.
You could update the select statement to look like this:
select case when exists(select * from sys.tables where name = 'TableName') then 1 else 0 end
The number represents the number of tables that match your like statement. For example, if you have the tables
Widgets
Products
WidgetsInProducts
And pass "Widgets" into your query, it's going to match both the table "Widgets" and "WidgetsInProducts". This is not the behavior you want.
To resolve this you need to do an exact match instead of a like as #Alex Aza demonstrated in his answer.
hi Lefteris Gkinis
if you do not want to change your query you can check your RecCount variable accordingly
say
if(RecCount == 0)
{
// code what you were using for false condition
}
else
{
// you got atleast one record
// and in RecCount you have number of matching rows
}
by this kind of code you are able to show matched row count also.
Related
I would like to create a new column in SQL using two conditions. I want to create a column that says 1 if the item count is greater than 1 and if item/sum is greater than 5, otherwise return 0. This is not my original data, is there anyway I could add this new column with these specified rows using a select statement.
First I want to say that using SQL key words or SQL function names as table name or column name should be avoided, so if possible, I recommend to rename the columns "number" and "sum".
The second point is it's unclear what should happen in case the sum column is 0. Since a division by zero is not possible, you will need to add a condition for that.
Anyway, the way to achieve such things is using CASE WHEN. So let's add the new column:
ALTER TABLE yourtable ADD column column_name INT;
Now, you need to execute an update command for that column providing the logic you want to apply. As an example, you can do this:
UPDATE yourtable SET column_name =
CASE WHEN item <= 1 THEN 0
WHEN sum = 0 THEN 1
WHEN item / sum > 0.5 THEN 1
ELSE 0 END;
This will set the new column to 1 only in case item is > 1 and sum is 0 or sum item / sum is > 0.5 (greater 50%). In all other cases it will be set to 0. Again, the bad column naming can be seen since "WHEN sum..." looks like you really build a sum and not just use a column.
If you want as example to set the new column to 0 instead of 1 when the sum is 0, just change it and try out.
In case you want to automatically apply this logic fur future inserts or updates, you can add a trigger on your new column. Something like this:
CREATE TRIGGER set_column_name
BEFORE INSERT ON yourtable
FOR EACH ROW
SET new.column_name = CASE WHEN new.item <= 1 THEN 0
WHEN new.sum = 0 THEN 1
WHEN new.item / new.sum > 0.5 THEN 1
ELSE 0 END;
But take care, the syntax of triggers depend on the DB you are using (this example will work in MYSQL). Since you did not tell us which DB you use, you maybe need to modify it. Furthermore, depending on your DB type and your requirements, you need zero, one or two triggers (for updates and for inserts).
I am attempting to filter my table and get the item that sold for the most amount of money. In order to do this I am using "AuctionOpen" to determine whether or not the auction is still open. The auction cannot be open and have the item been sold (later I will use this for the most expensive item available).
I am able to use the AND operator to compare AuctionOpen by using the following:
select s.*
from auctionsite.dbo.Auction s
where s.HighestBid = (select max(s2.HighestBid) from auctionsite.dbo.Auction
s2) and s.AuctionOpen = 0;
When I set this equal to zero I get results, but when I set it equal to 1, it only returns the column titles even though there are values set to 1 in the table.
Results when compared to 0:
Results when compared to 1:
Clearly, the highest bid is on a record where AuctionOpen <> 1.
I recommend using order by and fetch (or the equivalent in your database):
select s.*
from auctionsite.dbo.Auction s
where s.AuctionOpen = 0
order by s.HIghestBid desc
fetch first 1 row only
In SQL Server, use either select top (1) or offset 0 rows fetch first 1 row only.
I think you should try the Count aggregate function
here, try this:
**Select count(Item_name) As
[Item with the highest money]
from table_name
Group by Item_name DSEC;**
You can check my page hereSQL/MySQL tips for some SQL/MySQL lessons
Can I select a column based on another column's value being listed as a formula? So I have a table, something like:
column_name formula val
one NULL 1
two NULL 2
three one + two NULL
And I want to do
SELECT
column_name,
CASE WHEN formula IS NULL
val
ELSE
(Here's where I'm confused - How do I evaluate the formula?)
END as result
FROM
table
And end up with a result set like
column_name result
one 1
two 2
three 3
You keep saying column, and column name, but you're actually talking about rows, not columns.
The problem is that you (potentially) want different formulas for each row. For example, row 4 might be (two - one) = 1 or even (three + one) = 4, where you'd have to calculate row three before you could do row 4. This means that a simple select query that parses the formulas is going to be very hard to do, and it would have to be able to handle each type of formula, and even then if the formulas reference other formulas that only makes it harder.
If you have to be able to handle functions like (two + one) * five = 15 and two + one * five = 7, then you'd be basically re-implementing a full blown eval function. You might be better to return the SQL table to another language that has eval functions built in, or you could use something like SQL Eval.net if it has to be in SQL.
Either way, though, you've still got to change "two + one" to "2 + 1" before you can do the eval with it. Because these values are in other rows, you can't see those values in the row you're looking at. To get the value for "one" you have to do something like
Select val from table where column_name = 'one'
And even then if the val is null, that means it hasn't been calculated yet, and you have to come back and try again later.
If I had to do something like this, I would create a temporary table, and load the basic table into it. Then, I'd iterate over the rows with null values, trying to replace column names with the literal values. I'd run the eval over any formulas that had no symbols anymore, setting the val for those rows. If there were still rows with no val (ie they were waiting for another row to be done first), I'd go back and iterate again. At the end, you should have a val for every row, at which point it is a simple query to get your results.
Possible solution would be like this kind....but since you mentioned very few things so this works on your above condition, not sure for anything else.
GO
SELECT
t1.column_name,
CASE WHEN t1.formula IS NULL
t1.val
ELSE
(select sum(t2.val) from table as t2 where t2.formula is not null)
END as result
FROM
table as t1
GO
If this is not working feel free to discuss it further.
I am trying to automatically count the unique occurrences of a string saved in the table. Currently I have a count of a string but only when a user selects the string and it gives every record the same count value.
For example
Below is a image of my current table:
From the image you can see that there is a Requirement column and a count column. I have got it to the point were when the user would select a requirement record (each requirement record has a link) it would insert the requirement text into a requirement item called 'P33_REQUIREMENT' so the count can have a value to compare to.
This is the SQL that I have at current:
SELECT (SELECT COUNT(*)
FROM DIA_ASSOCIATED_QMS_DOCUMENTS
WHERE REQUIREMENT = :P33_REQUIREMENT
group by REQUIREMENT
) AS COUNT,
DPD.DIA_SELECTED,
DPD.Q_NUMBER_SELECTED,
DPD.SECTION_SELECTED,
DPD.ASSIGNED_TO_PERSON,
DAQD.REFERENCE,
DAQD.REQUIREMENT,
DAQD.PROGRESS,
DAQD.ACTION_DUE_DATE,
DAQD.COMPLETION_DATE,
DAQD.DIA_REF,
DA.DIA,
DA.ORG_RISK_SCORE
FROM DIA_PROPOSED_DETAIL DPD,
DIA_ASSOCIATED_QMS_DOCUMENTS DAQD,
DIA_ASSESSMENTS DA
WHERE DPD.DIA_SELECTED = DAQD.DIA_REF
AND DPD.DIA_SELECTED = DA.DIA
This is the sql used to make the table in the image.
This issue with this is, it is giving every record the same count when the user selects a requirement value. I can kind of fix this by also adding in AND DIA_SELECTED = :P33_DIA into the where clause of the count. DIA_SELECTED being the first column in the table and :P33_DIA being the item that stores the DIA ref number relating to the record chosen.
The output of this looks like:
As you can see there is only one count. Still doesn't fix the entire issue but a bit better.
So to sum up is there a way to have the count, count the occurrences individually and insert them in the requirements that are the same. So if there are three tests like in the images there would be a '3' in the count column where requirement = 'test', and if there is one record with 'test the system' there would be a '1' in the count column.
Also for more context I wont know what the user will input into the requirement so I can't compare to pre-determined strings.
I'm new to stack overflow I am hoping I have explained enough and its not too confusing.
The following extract:
SELECT (SELECT COUNT(*)
FROM DIA_ASSOCIATED_QMS_DOCUMENTS
WHERE REQUIREMENT = :P33_REQUIREMENT group by REQUIREMENT ) AS COUNT
Could be replaced by
SELECT (SELECT COUNT(*)
FROM DIA_ASSOCIATED_QMS_DOCUMENTS
WHERE REQUIREMENT = DAQD.REQUIREMENT ) AS COUNT
Which would give you - for each line, the number of requirements that are identical.
I'm not completely certain it is what you are after, but if it isn't, it should give you some ideas on how to progress (or allow you to indicate where I failed to understand your request)
I have the following query that is part of a common table expression. I don't understand the function of the "Select -1" statement. It is obviously different than the "Select 1" that is used in "EXISTS" statements. Any ideas?
select days_old,
count(express_cd),
count(*),
case
when round(count(express_cd)*100.0/count(*),2) < 1 then '0'
else ''
end ||
cast(decimal(round(count(express_cd)*100.0/count(*),2),5,2) as varchar(7)) ||
'%'
from foo.bar
group by days_old
union all
select -1, -- Selecting the -1 here
count(express_cd),
count(*),
case
when round(count(express_cd)*100.0/count(*),2) < 1 then '0'
else ''
end ||
cast(decimal(round(count(express_cd)*100.0/count(*),2),5,2) as varchar(7)) ||
'%'
from foo.bar
where days_old between 1 and 7
It's just selecting the number "minus one" for each row returned, just like "select 1" will select the number "one" for each row returned.
There is nothing special about the "select 1" syntax uses in EXISTS statements by the way; it's just selecting some random value because EXISTS requires a record to be returned and a record needs data; the number 1 is sufficient.
Why you would do this, I have no idea.
When you have a union statement, each part of the union must contain the same columns. From what I read when I look at this, the first statement is giving you one line for each days old value and then some stats for each day old. The second part of the union is giving you a summary of all the records that are only a week or so less. Since days old column is not relevant here, they put in a fake value as a placeholder in order to do the union. OF course this is just a guess based on reading thousands of queries through the years. To be sure, I would need to actually run teh code.
Since you say this is a CTE, to really understand why this is is happening, you may need to look at the data it generates and how that data is used in the next query that uses the CTE. That might answer your question.
What you have asked is basically about a business rule unique to your company. The true answer should lie in any requirements documents for the original creation of the code. You should go look for them and read them. We can make guesses based on our own experience but only people in your company can answer the why question here.
If you can't find the documentation, then you need to talk (Yes directly talk, preferably in person) to the Stakeholders who use the data and find out what their needs were. Only do this after running the code and analyzing the results to better understand the meaning of the data returned.
Based on your query, all the records with days_old between 1 and 7 will be output as '-1', that is what select -1 does, nothing special here and there is no difference between select -1 and select 1 in exists, both will output the records as either 1 or -1, they are doing the same thing to check whether if there has any data.
Back to your query, I noticed that you have a union all and compare each four columns you select connected by union all, I am guessing your task is to get a final result with days_old not between 1 and 7 and combine the result with day_old, which is one because you take all between 1 and 7.
It is just a grouping logic there.
Your query returns aggregated
data (counts and rounds) grouped by days_old column plus one more group for data where days_old between 1 and 7.
So, -1 is just another additional group there, it cannot be 1 because days_old=1 is an another valid group.
result will be like this:
row1: days_old=1 count(*)=2 ...
row2: days_old=3 count(*)=5 ...
row3: days_old=9 count(*)=6 ...
row4: days_old=-1 count(*)=7