I converted an Excel file into a text file, then imported this text file into a SQL Server database using the SQL Server import/export wizard tool. I found IS NULL not working in the where clause on one column (see the following):
WHERE ID IS NULL;
BTW, ID column's data type is varchar(50) with null as the default.
Does anybody have any idea why IS NULL does not work here?
The import probably loaded the values as empty strings into of as NULL. To handle this, change WHERE ID IS NULL to WHERE ID = ''
If you want them to be NULL, you can change them:
UPDATE Your_Table SET ID = NULL WHERE ID = ''
David's answer is most likely what you need, but for completeness... Are the values truly NULL or are they 'null' ?
Test:
SELECT TOP 5 * FROM TABLE WHERE ID IS NULL
Test:
SELECT TOP 5 * FROM TABLE WHERE ID='null'
If the latter returns results, then the string 'null' was stored, not an actual absent/NULL value.
You can set them to NULL as follows:
UPDATE T
SET ID=NULL
FROM TABLE T
WHERE ID='null'
If neither returned data, then find what is there... maybe they're all legit values.
SELECT COUNT(2), ID
FROM TABLE
GROUP BY ID
ORDER BY ID
--HAVING COUNT(2)>1 /* uncomment this line if too much comes back... */
Then decide how to proceed...
Related
I'm trying to clean the related records when type value is empty, please see below sample data:
session
Type
123
456
pdp
I've written below:
select *
from table
where Type is not null
However the "is not null" didn't clean empty record, it still returns the exact same sample table. Any suggestions how to make it right? Thanks.
select * from table where Type is not null or TRIM(Type) = ''
In this case, the value is not null, it is empty rather than null.
Answer my own question, can use length (Page_Type) > 0 to workaround
I have an excel spreadsheet with 15 or so fields. Wat I'm doing is, i open it, grab a row of data, then check each row for a value. Then using a few criteria I go look up to see if this Client value is already in the DB. As Example
Some of the fields mind be empty. Basically after checking some of the fields, I use them to check if that record exists already in DB. the problem arises when some fields are empty in which case when I query sql server it looks something like...
Select * from TblA where Company='Apple' and CompanyAdd ='Cupertino' and City=''
Because City = '' - it doesnt not find anything in SQL. The only thing that works is
and City is NULL
How am I able to programmatically assign that to a variable like CITY?
it is a string and the field in SQL is varchar
EDIT:
I want to be able to do something like this..... (as example)
if city = "" then
'I need this here to be so that....
city IS NULL
End if
So that when I query db it looks something like...
Select count(*) from TblA where City is Null
Is somethng like that possible?
You can use COALESCE for this purpose.
SELECT *
FROM TblA
WHERE COALESCE(Company, '')='Apple'
AND COALESCE(CompanyAdd, '') = 'Cupertino'
AND COALESCE(City, '') = ''
Keep in mind that the performance of this query will most likely not be stellar.
I've been banging my head against a brick wall for this for ages.
I am trying to query a table in SQL Express 2010. There are about ten fields in the table. One of the fields is a text field. Some of these have text in them, some have none (I am presuming that they are empty rather than null because querying with Is Null returns an empty set). I want to return the records which have text in this field and not those which are empty. I am guessing that they are empty rather than a blank space.
I have tried the NullIf and IsNull combinations I have seen posted in a few forums but the syntax in these are causing errors. When I put in ' ' as the empty string it is highlighted in red as an error and executing the query just returns an error about can not find such and such with this column name. Sorry I don't have the exact phrase, I'm also having problems with a monitor, etc, etc...
Hope you can help, let me know if you need any more info.
Thanks!
This bit of code shows how to handle NULL and/or "emptry string" text fields:
CREATE TABLE #TextTest (
ID INT IDENTITY,
TextCol TEXT
)
--Add 2 rows with data, 1 with NULL, 1 with "empty string".
INSERT INTO #TextTest (TextCol)
VALUES ('123'),('456'), (NULL), ('')
--This should succeed, but returns the one row with the "empty string".
SELECT *
FROM #TextTest
WHERE TextCol IS NOT NULL
--This should fail
SELECT *
FROM #TextTest
WHERE TextCol <> ''
--This should succeed.
SELECT *
FROM #TextTest
WHERE CAST(TextCol AS VARCHAR(MAX)) <> ''
--Clean up temp table when finished.
--DROP TABLE #TextTest
NOTE: ntext, text, and image data types will be removed in a future version of Microsoft SQL Server. Avoid using these data types in new development work, and plan to modify applications that currently use them. Use nvarchar(max), varchar(max), and varbinary(max) instead.
I understand that AS is used to create an alias. Therefore, it makes sense to have one long name aliased as a shorter one. However, I am seeing a SQL query NULL as ColumnName
What does this imply?
SELECT *, NULL as aColumn
Aliasing can be used in a number of ways, not just to shorten a long column name.
In this case, your example means you're returning a column that always contains NULL, and it's alias/column name is aColumn.
Aliasing can also be used when you're using computed values, such as Column1 + Column2 AS Column3.
When unioning or joining datasets using a 'Null AS [ColumnA] is a quick way to make sure create a complete dataset that can then be updated later and a new column does not need to be created in any of the source tables.
In the statement result we have a column that has all NULL values. We can refer to that column using alias.
In your case the query selects all records from table, and each result record has additional column containing only NULL values. If we want to refer to this result set and to additional column in other place in the future, we should use alias.
It means that "aColumn" has only Null values. This column could be updated with actual values later but it's an empty one when selected.
---I'm not sure if you know about SSIS, but this mechanism is useful with SSIS to add variable value to the "empty" column.
When using SELECT you can pass a value to the column directly.
So something like :
SELECT ID, Name, 'None' AS Hobbies, 0 AS NumberOfPets, NULL AS Picture, '' AS Adress
Is valid.
It can be used to format nicely a query output when using UNION/UNION ALL.
Query result can have a new column that has all NULL values. In SQL Server we can do it like this
SELECT *, CAST(NULL AS <data-type>) AS as aColumn
e.g.
SELECT *, CAST(NULL AS BIGINT) AS as aColumn
How about without using the the as
SELECT ID
, Name
, 'None' AS Hobbies
, 0 AS NumberOfPets
, NULL Picture
Usually adding NULL as [Column] name at the end of a select all is used when inserting into another table a calculated column based on the table you have just selected.
UPDATE #TempTable SET aColumn = Column1 + Column2 WHERE ...
Then exporting or saving the results to another table.
imagine there are 50 columns. I dont wan't any row that includes a null value. Are there any tricky way?
SQL 2005 server
Sorry, not really. All 50 columns have to be checked in one form or another.
Column1 IS NOT NULL AND ... AND Column50 IS NOT NULL
Of course, under these conditions why not disallow NULLs in the first place by having NOT NULL in the table definition
If it's SQL Server 2005+ you can do something like:
SELECT fields
FROM MyTable
WHERE stuff
EXCEPT -- This excludes the below results
SELECT fields
FROM MyTable
WHERE (Col1 + Col2 + Col3....) IS NULL
Adding a null to a value results in a null, so the sum of all your columns will be NULL.
This may need to change based on your data types, but adding NULL to either a char/varchar or a number will result in another NULL.
If you are looking at the values not being null, you can do this in the select statement.
SELECT ISNULL(firstname,''), ISNULL(lastname,'') FROM TABLE WHERE SOMETHING=1
This will replace nulls with string blanks. If you want another value use: ISNULL(firstname,'empty') for example. You can use anything where the word empty is.
I prefer this query
select *
from table
where column1>''
and column2>''
and (column3>'' or column3<'')
Allows sql server to use an index seek if the proper index/es exist. you would have to do the syntext for column 3 for any numeric values that could be negative.