I currently have a sql statement that outputs data into an excel document. However, every time there is a cell that doesn't have data, it outputs NULL into the cell. I was wondering if there was a way that I could replace NULL with just a blank space? Someone suggested using coalesce to do this, however I haven't ever had the chance to use it so I will have to do some reading on it. Anyone have any other suggestions?
In your select you can put an IsNull/IfNull round the column. Not particularly efficient but does what you want.
MS SQL
Select IsNull(ColName, '') As ColName From TableName
MySQL
Select IfNull(ColName, '') As ColName From TableName
IFNULL is an Oracle extension (adopted by many other platforms). The "standard" SQL function is coalesce():
SELECT COALESCE(columnName, ' ') AS ColumnName
FROM tableName;
Microsoft SQL
UPDATE TABLE_NAME
SET COLUMN_NAME = ''
WHERE COLUMN_NAME IS NULL
NOTE: this will SET, not select the result in your TABLE
MySQL
select IFNULL(columnName, '') from tableName
IFNULL(expr1,expr2)
If expr1 is not NULL, IFNULL() returns expr1; otherwise it returns expr2. IFNULL() returns a numeric or string value, depending on the context in which it is used.
SELECT teacher.name, IfNull(dept.name, '') as Dept
FROM teacher left outer JOIN dept
ON teacher.dept=dept.id
Related
The results of my SQL query include null values. How do I filter out null values?
The syntax may vary depending on the database you are using but you can explicitly exclude nulls in the where clause. For example, the following will exclude null values in the primary_author field:
SELECT
date,
primary_author,
ISBN
FROM
books
WHERE
primary_author IS NOT NULL;
My example works on every database I know, so it should work for you =)
SELECT *
FROM TABLE_NAME
WHERE COLUMN_NAME IS NOT NULL
Here you can find a simple explanation and some examples: https://www.w3schools.com/sql/sql_null_values.asp
But some times you want to replace null values for a default value, like 'X', in this case, we should know the database for correct syntax, here some examples:
Oracle:
SELECT nvl(column_name,'X')
FROM TABLE_NAME
Sqlite:
SELECT ifnull(column_name,'X')
FROM TABLE_NAME
SqlServer:
SELECT coalesce(column_name,'X')
FROM TABLE_NAME
SELECT column_name1,column_name2,column_name3,column_name4 from table_name
How do i do multiple checks for all the coulmn_name?
for now i am checking for NULL to return "Empty String" using COALESCE.
SELECT
COALESCE(column_name1,'')as Column_name1,
COALESCE(column_name2,'')as Column_name2,
COALESCE(column_name3,'')as Column_name3,
COALESCE(column_name4,'')as Column_name4, from table_name
My requirement is to return "Empty String" where ever the values are NULL or WhiteSpaces or NA.
Thanks in advance.
One method uses case:
select (case when column_name1 is null or ltrim(rtrim(column_name1)) in ('NA', '') then ''
else column_name1
end)
CASE, ISNULL, COALESCE can all be used in combination as necessary.
If you are using the 2012 or later versions of SQL Server, there are 2 more options to choose from to simplify CASE statement:
1. IIF
2. CHOOSE
Check this link for more details
SELECT coalesce (nullif (rtrim(ltrim(column_name1)), 'N/A'), '')
AS column_name1
FROM table_name
Found an answer.. is this correct way?? i mean does this works exactly to the requirement?
I have a table which has a `department` column (allows null) but when I select that table and the field is null I don't want it to show Null but "-".
I'm told to put the if statement inside the select statement but I can't figure it out. How can I do this?
You want to use the function coalesce():
select coalesce(department, '-')
from table t
This is an ANSI standard function available in most databases.
You can use two methods:
1. Using CASE:
SELECT CASE WHEN department IS NULL
THEN '-'
ELSE department
END AS department FROM TableName
CASE evaluates a list of conditions and returns one of multiple possible result expressions. Read more here.
2. Using COALESCE:
SELECT COALESCE (department,'-') FROM TableName
COALESCE returns first parameter which is not null. Read more here.
You need to use the 'CASE WHEN' statement in your select query. Like this:
SELECT CASE WHEN Department IS NULL THEN Department = '-'
END AS DEPARTMENT
FROM Table_Name
You can use following code:
select ISNULL(department, '-') AS DEPARTM
from dbo.tbl_Department
I have a simple SQL query (SQL Server 2005) where I'm selecting from a table that contains multiple columns that have BIT values.
These columns are nullable so can contain NULL, 0 or 1.
There are a fair number of these columns and in my query I want to return zero if the value is NULL.
I'm currently using ISNULL like so:
SELECT Name, Age, ISNULL(LikesOranges,0), ISNULL(LikesApples,0), ISNULL(LikesPears,0)
FROM FoodPreferences
As I've mentioned, there are a lot of these BIT columns (much more than in the simple example above).
Is there a way I can use ISNULL over multiple columns like this:
SELECT ISNULL(*,0) FROM FoodPreferences
The above query doesn't work but you get what I'm trying to do - so I can avoid having to write an ISNULL statement for each column,
Thanks.
Try this:
SELECT COALESCE(LikesOranges, LikesApples, LikesPears) AS MyBit FROM FoodPreferences
This will return the first non-null value. If all fields are NULL the result is NULL.
UPDATE:
And the conclusion is:
SELECT ISNULL(COALESCE(LikesOranges, LikesApples, LikesPears),0) AS MyBit FROM FoodPreferences
so I can avoid having to write an
ISNULL statement for each column,
Run this query and copy the result to your select statement. system_type_id = 104 filters the result on bit columns.
select stuff((select ', isnull('+name+', 0)'
from sys.columns
where object_id = object_id('FoodPreferences') and
system_type_id = 104
for xml path('')), 1, 1, '')
Result:
-------------------------------------------------------------------------
isnull(LikesOranges, 0), isnull(LikesApples, 0), isnull(LikesPears, 0)
I don't think so. But an option might be to create a view onto that table and put all the ISNULL statements in the view. At least then you won't have to do it every time
eg.
CREATE VIEW vwFoodPreferences
AS
SELECT Name,
Age,
ISNULL(LikesOranges,0) AS LikesOranges,
ISNULL(LikesApples,0) AS LikesApples,
ISNULL(LikesPears,0) AS LikesPears
FROM FoodPreferences
Unfortunately, the simple answer is no.
You could write sql dynamically, but whatever happens, the final resulting sql would have to be ISNULL(a,0), ISNULL(b,0), ISNULL(c,0), ISNULL(d,0), etc
i think you can write a simple program and generate select clause by reading all columns and generating the select
while not this :
SELECT COALESCE(LikesOranges, LikesApples, LikesPears, 0) AS MyBit FROM FoodPreferences
https://learn.microsoft.com/en-us/sql/t-sql/language-elements/coalesce-transact-sql?view=sql-server-2017
How do you write a SELECT statement that only returns rows where the value for a certain column is null?
Do you mean something like:
SELECT COLUMN1, COLUMN2 FROM MY_TABLE WHERE COLUMN1 = 'Value' OR COLUMN1 IS NULL
?
I'm not sure if this answers your question, but using the IS NULL construct, you can test whether any given scalar expression is NULL:
SELECT * FROM customers WHERE first_name IS NULL
On MS SQL Server, the ISNULL() function returns the first argument if it's not NULL, otherwise it returns the second. You can effectively use this to make sure a query always yields a value instead of NULL, e.g.:
SELECT ISNULL(column1, 'No value found') FROM mytable WHERE column2 = 23
Other DBMSes have similar functionality available.
If you want to know whether a column can be null (i.e., is defined to be nullable), without querying for actual data, you should look into information_schema.
Use Is Null
select * from tblName where clmnName is null
You want to know if the column is null
select * from foo where bar is null
If you want to check for some value not equal to something and the column also contains null values you will not get the columns with null in it
does not work:
select * from foo where bar <> 'value'
does work:
select * from foo where bar <> 'value' or bar is null
in Oracle (don't know on other DBMS) some people use this
select * from foo where NVL(bar,'n/a') <> 'value'
if I read the answer from tdammers correctly then in MS SQL Server this is like that
select * from foo where ISNULL(bar,'n/a') <> 'value'
in my opinion it is a bit of a hack and the moment 'value' becomes a variable the statement tends to become buggy if the variable contains 'n/a'.
select Column from Table where Column is null;
select * from tableName where columnName is null
For some reasons IS NULL may not work with some column data type. I was in need to get all the employees that their English full name is missing, I've used:
SELECT emp_id, Full_Name_Ar, Full_Name_En
FROM employees
WHERE Full_Name_En = '' or Full_Name_En is null