How to comabine Column1,Column2(Column3) and in the column 3 I had some NULLS. Instead of Nulls I need Column1,Column2
Select concat(column1, Column2, Column3) Concatenatedvalue from table1.
I assumed this is SQL server, concat will take care of null values . Please make sure not to use null values because CONCAT_NULL_YIELDS_NULL will be ON as default settings for most of the databases as long as it is not changed.
My database has CONCAT_NULL_YIELDS_NULL ON feature.
SELECT 'abc' + NULL fromplus , concat('ABC', Null) fromconcat ;
Output:
fromplus fromconcat
NULL ABC
If you see I got null from '+' and valid value from concat.
Related
My sql query working fine but i have another issue some rows in my table have NULL values. i want to remove all NULL valued rows. Any recommendations?
Delete statement should work
DELETE FROM your_table
WHERE your_column IS NULL;
In case of multi column NULL check, I suggest using COALESCE
DELETE FROM your_table
WHERE COALESCE (your_column1, your_column2, your_column3 ) IS NULL;
If you want to delete a row where all columns values are null then use following query to delete:
DELETE FROM your_table
where your_column1 IS NULL
AND your_column2 IS NULL
AND your_column3 IS NUL;
But if you want to delete a row where any column value is null then use following query to delete:
DELETE FROM your_table
where your_column1 IS NULL
OR your_column2 IS NULL
OR your_column3 IS NUL;
You could start by filtering out columns you don't need, want, or will not use.
SELECT column1, column2, column3
FROM table
Then to remove the null values from your queries, use the IS NOT NULL command. Remember, null values can also be zeros, depending on how your tables and the data formats have been set up. In the example below, assume column2 is a number format.
WHERE column1 IS NOT NULL AND column2 > 0 AND column3 IS NOT NULL
I'm running a simple 'WHERE [COLUMN] IS NULL' statement but the expected row that I wanted was not retrieved. I also did a distinct values statement and there were 7 different NULLs.
Is there an explanation for this and is there a way to fix this?
Basically all comparison operators with NULL return "false" or NULL which are filtered out in a WHERE clause.
So, your query should be:
WHERE COLUMN <> 'VALUE' OR COLUMN IS NULL
alternatively use COALESCE()
WHERE COALESCE(column, '') <> 'A'
I want to compare multiple column's NULL values. eg. Assume I have 3 columns in my table from which I have to find out NOT NULL values. I am using following code :
select * from table1 where
column1 is not null
and column2 is not null
and column3 is not null
I don't want to use this code as it uses "and" multiple times if columns goes on increasing.
Anybody have option to this in Oracle 11g ?
I agree with the comment that your query is fine as is. If the columns that you are checking are all of a numeric variety then you can use Oracle's behavior with null values to your advantage to shorten the query like this:
select * from table 1
where
(
column1
+ column2
+ column3
) is not null;
If any of the listed columns are null then the sum will be null also. Unfortunately, if you have strings instead--null strings concatenate just fine, so the same approach doesn't work with them.
You can use
COALESCE (expr1, expr2)
which is equivalent to
CASE WHEN expr1 IS NOT NULL THEN expr1 ELSE expr2 END
Your syntax would be
coalesce(column1,....,columnn) is not null
You can use this instead of the COALESCE:
SELECT *
FROM table1
WHERE column1 || column2 || column3 || column4 IS NOT NULL;
Tim Rhyne answers well. If you had all string columns, your where clause could be:
WHERE LENGTH(COLUMN1)+LENGTH(COLUMN2)+LENGTH(COLUMN3) IS NOT NULL
If you had a mix of string and numeric:
WHERE COLUMN_INTEGER1+COLUMN_INTEGER2+LENGTH(COLUMN_STRING3) IS NOT NULL
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.
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