What is the difference between distinct and GROUP BY?
Distinct is used to find unique/distinct records where as a group by is used to group a selected set of rows into summary rows by one or more columns or an expression. Group By operator is meant for aggregating/grouping rows where as distinct is just used to get distinct values.
Should I use distinct or GROUP BY?
DISTINCT is used to filter unique records out of the records that satisfy the query criteria. The “GROUP BY” clause is used when you need to group the data and it should be used to apply aggregate operators to each group.
Which is quicker distinct or GROUP BY?
DISTINCT creates a temporary table and uses it for storing duplicates. GROUP BY does the same, but sortes the distinct results afterwards. is faster, if you don’t have an index on profession .
What is GROUP BY in DB2?
The GROUP BY clause allows you to find the characteristics of groups of rows rather than individual rows. When you specify a GROUP BY clause, SQL divides the selected rows into groups such that the rows of each group have matching values in one or more columns or expressions.
Can we use distinct and GROUP BY in same query?
A DISTINCT and GROUP BY usually generate the same query plan, so performance should be the same across both query constructs. GROUP BY should be used to apply aggregate operators to each group. If all you need is to remove duplicates then use DISTINCT.
What is difference between order by and group by?
The Group By clause is used to group data based on the same value in a specific column. The ORDER BY clause, on the other hand, sorts the result and shows it in ascending or descending order. It is mandatory to use the aggregate function to use the Group By.
How do I remove duplicates by GROUP BY?
The group by clause can also be used to remove duplicates. The go to solution for removing duplicate rows from your result sets is to include the distinct keyword in your select statement. It tells the query engine to remove duplicates to produce a result set in which every row is unique.
How do you remove duplicates 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.
When to use group by in DB2 SELECT DISTINCT?
If you want to select distinct values of some columns in the select list, you should use the GROUP BY clause. In case a column contains multiple NULL values, DISTINCT will keep only one NULL in the result set. Db2 SELECT DISTINCT examples. We will use the authors table from the sample database for the demonstration.
What’s the difference between distinct and group by?
Essentially, DISTINCT collects all of the rows, including any expressions that need to be evaluated, and then tosses out duplicates. GROUP BY can (again, in some cases) filter out the duplicate rows before performing any of that work.
When to use the DISTINCT keyword in SQL?
Code language: SQL (Structured Query Language) (sql) The DISTINCT keyword is applied to all columns. It means that the query will use the combination of values in all columns to evaluate the distinction. If you want to select distinct values of some columns in the select list, you should use the GROUP BY clause.
Is there a way to SELECT DISTINCT values?
If you want to select distinct values of some columns in the select list, you should use the GROUP BY clause. In case a column contains multiple NULL values, DISTINCT will keep only one NULL in the result set.