I have a table PATIENT with Column STATUS. When I queried to get STATUS not equal to 1, I was expecting the result as NULL and 2.
But I am only getting 2 as the result. Can someone help me with this?
CREATE TABLE #PATIENT
(STATUS INT)
INSERT INTO #PATIENT (STATUS)
SELECT 1
UNION
SELECT 2
UNION
SELECT NULL
SELECT * FROM #PATIENT WHERE STATUS <> 1
When I queried with
SELECT * FROM #PATIENT WHERE ISNULL(STATUS, 0) != 1
I am able to get NULL and 2 as the result.
This is SQL SERVER 2012.
You can use OR in WHERE with Condition STATUS IS NULL .
SELECT * FROM #PATIENT WHERE STATUS <> 1 OR STATUS IS NULL
This will do it.
EDIT:
Conceptually, NULL means “a missing unknown value” and it is
treated somewhat differently from other values.
You cannot use arithmetic comparison operators such as =, <, or <>
to test for NULL
Because the result of any arithmetic comparison with NULL is also
NULL, you cannot obtain any meaningful results from such comparisons
we can not equate or not equate anything with null, thats why IS NULL
SELECT NULL <> 1 ===> NULL
Even though it is supposed to be true, it will return `NULL`
Hope this helps.
When you compare NULL value to any value then the result is always NULL.
So if you wan to select the NULL value as well then try this:
SELECT * FROM #PATIENT WHERE STATUS <> 1 OR STATUS IS NULL
DEMO
Conceptually "NULL" means a missing value. To test for NULL IS NULL or IS NOT NULL condition is used. Arithmetic operators cannot be used for comparing NULL values.
NULL<>1 :: returns false because NULL can be 1 or any other value (an unknown value).
Null is a special marker used in Structured Query Language (SQL) to indicate that a data value does not exist in the database.
And reason because you got only 2 and NOT NULL is because in SQL nothing is equal to NULL but also nothing is NOT equal to NULL.
In Simple words you cannot equate and not equate any value with NULL.
I want to generate a SQL query to get null count in a particular column like
SELECT COUNT (column) AS count
FROM table
WHERE column = null ;
This is returning 0, but I want how many null values are present in that column like
SELECT COUNT (column) AS count
FROM table
WHERE column = 'some value';
which returns the count of the matched records
NULL value is special in that you cannot use = with it; you must use IS NULL instead:
SELECT COUNT (*) AS count FROM table where column IS null ;
This is because NULL in SQL does not evaluate as equal to anything, including other NULL values. Also note the use of * as the argument of COUNT.
You can use a conditional sum()
SELECT sum(case when column is null
then 1
else 0
end) AS count
FROM table
A different query but exact answer check it out
select count(*)-count(column) from table
please vote check this as answer if it helps you
To get exact output you can use below command as well -
SELECT COUNT (*) AS count FROM table where column IS null OR column='';
because some times only '' doesn't counted as NULL.
I have 2 tables (stud and stud1). Both having 2 columns but stud1 contains 1 record which is null.
I have created following 2 queries.First one is returning the accurate result but other one which is using not in returning nothing. I guess that is because of the null value. But I don't understand the reason for it. Can someone help me with this?
See NOT IN clause and NULL values.
That's because your 2nd query equals:
SELECT * FROM #stud
WHERE ID <> NULL
When ansi_nulls is on, ID <> NULL is unknown, so you won't get any rows.
Let's say I want to display all items in a table with following criteria how would i do this?
SELECT *
FROM TABLE
WHERE TABLE.COLUMN1 = 'example' AND TABLE.COLUMN2 != 'NULL'
I want it to display all values from COLUMN1. How does one go about this process in MS SQL?
NULL values can be compared using IS [NOT] NULL in SQL server. Please check this.
SELECT *
FROM TABLE
WHERE TABLE.COLUMN1 = 'example' AND TABLE.COLUMN2 IS NOT NULL
NULL is an UNKNOWN value , you cannot use any Comparison Operators (= , <> , > , <) with it. you check for nulls like
ColumnName IS NULL or ColumnName IS NOT NULL
If you think about it , it makes sense, to compare two or more values, you need to know the values only then you can compare them, Since SQL Server considers a NULL to be an UNKNOWN value, you cannot really compare an unknown value to anything.
I have created a table called table1 and it has 4 columns named Name,ID,Description and Date.
I have created them like Name varchar(50) null, ID int null,Description varchar(50) null, Date datetime null
I have inserted a record into the table1 having ID and Description values. So Now my table1 looks like this:
Name ID Description Date
Null 1 First Null
One of them asked me to modify the table such a way that The columns Name and Date should have Null values instead of Text Null. I don't know what is the difference between those
I mean can anyone explain me the difference between these select statements:
SELECT * FROM TABLE1
WHERE NAME IS NULL
SELECT * FROM TABLE1
WHERE NAME = 'NULL'
SELECT * FROM TABLE1
WHERE NAME = ' '
Can anyone explain me?
In a CREATE TABLE, the NULL or NOT NULL here varchar(50) null is a constraint that determines whether NULLs are allowed. NOT NULL means no.
When you inserted data, which statement did you run?
INSERT TABLE1 VALUES (Null, 1, First, Null)
or
INSERT TABLE1 VALUES ('Null', 1, First, 'Null')
The first one uses the keyword NULL, inserts a NULL (not a null value: no such thing, arguably). No values is stored except in the NULL bitmap fields
The second one has a string "null" and the characters N, U, L, L + 2 bytes for length are stored
When you run SELECT * FROM TABLE1, client tools will show NULL.
To test whether you actually have NULLs or the string NULL, run this
SELECT ISNULL(name, 'fish'), ISNULL(date, GETDATE()) FROM TABLE1
For the SELECTs
--null symbols. No value stored
SELECT * FROM TABLE1 WHERE NAME IS NULL
--string null
SELECT * FROM TABLE1 WHERE NAME = 'NULL'
--empty string
SELECT * FROM TABLE1 WHERE NAME = ' '
Note: null symbol/value is not empty string. It has no value and won't compare. Even to itself.
As for your DBA, the code above with ISNULL will decide what is stored.
Edit: if you are storing null symbol/value, then your DBA should read up on "null bitmap"
The data does represent nulls. The text 'Null' is your query tool displaying the text.
One of them asked me to modify the table such a way that The columns Name and Date should have Null values instead of Text Null. I don't know what is the difference between those.
The NULL keyword indicates the absence of any value -- the value is unknown.
But that won't stop someone from storing the letters that spell out "NULL", data type providing (which INT and DATETIME will not). Because of this, operators like IS NULL would not work on text that spells out "NULL" and vice versa -- searching for strings using: ... LIKE '%NULL%' will not return records with NULL values.
The data type of the column does matter with regard to NULL in SQL Server. In a UNION statement, you need to cast NULL to be the appropriate data type -- the default for NULL is INT:
SELECT CAST('2011-01-01 00:00:00' AS DATETIME)
UNION
SELECT CAST(NULL AS DATETIME)
Based on the information provided about the columns and the output, the DBA appears to be asking you to change the text the client you are using to connect to SQL Server with displays when a NULL value is encountered in a resultset. Reminds me of my first job dishwashing, and was asked to get the lefthanded spatula...
The string "Null" is a string.
The value of NULL (or Null or null, SQL is case-insensitive when it comes to these things) is used to denote an unknown value. It's the empty set of values, if you will.
http://www.w3schools.com/sql/sql_null_values.asp
NULL, in software, is symbolic of no value. Assuming you're inserting the columns using a string with null as the value, use the null constant. e.g.
INSERT INTO table1 (Name,ID,Description,Date) VALUES (NULL,1,'First',NULL);
Note that NULL is a constant in SQL, not the word "NULL" in a string.
AFAIC, there is no different between NULLs. There are different column types. But as long as a column is a text data type, and it's NULL, it's a text NULL.
Sometimes there are questions about empty strings ("") instead of NULLs, but the description you're using doesn't seem to be referring to that.
SELECT * FROM TABLE1 WHERE NAME IS NULL
Returns all rows where the Name is NULL
SELECT * FROM TABLE1 WHERE NAME = 'NULL'
Returns all rows where the Name is equal to the string 'NULL', Null values are not returned
SELECT * FROM TABLE1 WHERE NAME = ' '
Returns all rows where the Name is equal to exactly one space ' ', Null values are not returned
If you run this statement it might help clear up when its null and when its not
select
*,
case
WHEN name is null THEN 'Its Null alright'
ELSE 'It has a value'
END
FROM TABLE1