Is there a not distinct in SQL?
SQL has the is [not] null predicate to test if a particular value is null . With is [not] distinct from SQL also provides a comparison operator that treats two null values as the same. Note that you have to use the negated form with not to arrive at similar logic to the equals ( = ) operator.
What can I use instead of distinct in SQL?
6 Answers. GROUP BY is intended for aggregate function use; DISTINCT just removes duplicates (based on all column values matching on a per row basis) from visibility. If TABLE2 allows duplicate values associated to TABLE1 records, you have to use either option.
How do I stop distinct in SQL Server?
Put PKs (with Clustered Indexes) on your tables, and a FK relationship between them. Index CountryID in the Users table, and put a Unique Index on the Country field. Once you’ve done all that, using DISTINCT how you have will actually give you the ideal execution plan.
How do I select duplicates in SQL?
To select duplicate values, you need to create groups of rows with the same values and then select the groups with counts greater than one. You can achieve that by using GROUP BY and a HAVING clause.
Is not distinct from Firebird?
Description: Two operands are considered DISTINCT if they have a different value or if one of them is NULL and the other isn’t. They are NOT DISTINCT if they have the same value or if both of them are NULL . if (New. … The “ = ” and “ <> ” operators, by contrast, return NULL if one or both operands are NULL .
How do you check if a column is empty in SQL?
How do I check if a column is empty or null in MySQL?
- MySQL code: select isnull(mycolumn) from mytable returns 1 if mycolumn is null. – Eric Leschinski. …
- what about length(trim(mycolumn)) > 0 ? – Cyril Jacquart. …
- For MSSQL > WHERE COLUMN <> ” OR WHERE LEN(COLUMN) > 0 OR WHERE NULLIF(LTRIM(RTRIM(COLUMN)), ”) IS NOT NULL.
How do I select all rows in SQL?
Here’s the SQL query to select every nth row in MySQL. mysql> select * from table_name where table_name.id mod n = 0; In the above query, we basically select every row whose id mod n value evaluates to zero.
How do you select distinct rows in SQL without using distinct?
Below are alternate solutions :
- Remove Duplicates Using Row_Number. WITH CTE (Col1, Col2, Col3, DuplicateCount) AS ( SELECT Col1, Col2, Col3, ROW_NUMBER() OVER(PARTITION BY Col1, Col2, Col3 ORDER BY Col1) AS DuplicateCount FROM MyTable ) SELECT * from CTE Where DuplicateCount = 1.
- Remove Duplicates using group By.
What can I use instead of distinct in Oracle?
The DISTINCT operator causes Oracle to fetch all rows satisfying the table join and then sort and filter out duplicate values. EXISTS is a faster alternative, because the Oracle optimizer realizes when the subquery has been satisfied once, there is no need to proceed further and the next matching row can be fetched.
Why we should not use distinct in SQL?
If you are missing a join and using a GROUP BY, you’ll get back more information than you’re expecting. If you are missing a join and using DISTINCT the SQL engine will perform an unbounded (or partially bounded) join, narrow the results down, and then come up with the expected answer.
How can get second highest salary in SQL Server?
How To Find Second Highest Salary Using a Sub-Query
- SELECT TOP 1 SALARY.
- FROM (
- SELECT DISTINCT TOP 2 SALARY.
- FROM tbl_Employees.
- ORDER BY SALARY DESC.
- ) RESULT.
- ORDER BY SALARY.
Is select distinct bad practice?
As a general rule, SELECT DISTINCT incurs a fair amount of overhead for the query. Hence, you should avoid it or use it sparingly. The idea of generating duplicate rows using JOIN just to remove them with SELECT DISTINCT is rather reminiscent of Sisyphus pushing a rock up a hill, only to have it roll back down again.
Which is faster distinct or group by in SQL Server?
DISTINCT is used to filter unique records out of all records in the table. It removes the duplicate rows. SELECT DISTINCT will always be the same, or faster than a GROUP BY.