Well, GROUP BY and DISTINCT have their own use. GROUP BY cannot replace DISTINCT in some situations and DISTINCT cannot take place of GROUP BY. It is as per your choice and situation how you are optimizing both of them and choosing where to use GROUP BY and DISTINCT.

Can we use distinct and GROUP BY together in SQL?

• You can use it together in SELECT …, COUNT(DISTINCT …) …
• no, you can drop the DISTINCT , it’s redundant. …
• group by delivers distinct results. …
• A few weeks back, I was browsing through some articles and came across some discussion about some special use-case for this.

Is distinct and GROUP BY the same?

GROUP BY lets you use aggregate functions, like AVG , MAX , MIN , SUM , and COUNT . On the other hand DISTINCT just removes duplicates. This will give you one row per department, containing the department name and the sum of all of the amount values in all rows for that department.

Can distinct be used with 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. … The group by can also be used to find distinct values as shown in below query. The two queries return same result.

Can we use GROUP BY and having together?

While the GROUP BY Clause groups rows that have the same values into summary rows. The having clause is used with the where clause in order to find rows with certain conditions. The having clause is always used after the group By clause.

Can you use distinct in a join?

You can use CTE to get the distinct values of the second table, and then join that with the first table. You also need to get the distinct values based on LastName column. You do this with a Row_Number() partitioned by the LastName, and sorted by the FirstName.

Is distinct better than GROUP BY?

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.

Can we use distinct in having clause?

using Distinct with a Group BY is redudant, yes. But it doesnt solve the root problem. The root problem is that the HAVING clause counts the total number before the GROUP BY or the DISTINCT is operated on. Thus removing the DISTINCT will still cause an incorrect count.

Can we use distinct and GROUP BY Together in Oracle?

We can use GROUP BY without specifying any aggregate functions in the SELECT list. However, the same result is usually produced by specifying DISTINCT instead of using GROUP BY.

Can we use distinct in aggregate function?

DISTINCT can be used to return unique rows from a result set and it can be used to force unique column values within an aggregate function.

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What is difference between distinct and unique?

The main difference between unique and distinct is that UNIQUE is a constraint that is used on the input of data and ensures data integrity. While DISTINCT keyword is used when we want to query our results or in other words, output the data.

Should I use distinct?

If you’re querying a table that is expected to have repeated values of some field or combination of fields, and you’re reporting a list of the values or combinations of values (and not performing any aggregations on them), then DISTINCT is the most sensible thing to use.

What is difference between distinct and GROUP BY in mysql?

Distinct is used to filter unique records out of the records that satisfy the query criteria. Group by clause is used to group the data upon which the aggregate functions are fired and the output is returned based on the columns in the group by clause.

Can we use ORDER BY and GROUP BY in same query?

GROUP BY and ORDER BY can be used in the same query and it is NOT required that they be the same column. GROUP BY controls the way the data is organized for sumarization. ORDER BY simply sorts the rows of the result.

Which is most suitable scenario for the use of GROUP BY clause?

Hello! The GROUP BY clause is a SQL command that is used to group rows that have the same values.

What is the difference between GROUP BY and WHERE clause?

WHERE is used to filter records before any groupings take place that is on single rows. GROUP BY aggregates/ groups the rows and returns the summary for each group. HAVING is used to filter values after they have been groups.

Is distinct expensive?

In a table with million records, SQL Count Distinct might cause performance issues because a distinct count operator is a costly operator in the actual execution plan.

Does distinct affect performance?

Yes, basically it has to sort the results and then re-processed to eliminate the duplicates. This cull could also be being done during the sort, but we can only speculate as to how exactly the code works in the background. You could try and improve the performance by creating an index composed of all three (3) fields.

Does distinct reduce performance?

Yes, as using DISTINCT will (sometimes according to a comment) cause results to be ordered. Sorting hundreds of records takes time. Try GROUP BY all your columns, it can sometimes lead the query optimiser to choose a more efficient algorithm (at least with Oracle I noticed significant performance gain).

How do you distinct and count together in SQL?

The correct syntax for using COUNT(DISTINCT) is: SELECT COUNT(DISTINCT Column1) FROM Table; The distinct count will be based off the column in parenthesis. The result set should only be one row, an integer/number of the column you’re counting distinct values of.

How do I use distinct in one column in SQL?

Adding the DISTINCT keyword to a SELECT query causes it to return only unique values for the specified column list so that duplicate rows are removed from the result set. Since DISTINCT operates on all of the fields in SELECT’s column list, it can’t be applied to an individual field that are part of a larger group.

What is group by in SQL?

The GROUP BY Statement in SQL is used to arrange identical data into groups with the help of some functions. i.e if a particular column has same values in different rows then it will arrange these rows in a group. … GROUP BY clause is used with the SELECT statement.

Can we apply distinct on two columns?

Answer. Yes, the DISTINCT clause can be applied to any valid SELECT query. It is important to note that DISTINCT will filter out all rows that are not unique in terms of all selected columns.

Is SELECT distinct fast?

Most of the SELECT DISTINCT queries will perform exactly as fast as their simple SELECT counterparts, because the optimizer will do away with the step necessary for eliminating duplicates.

Which one is faster distinct or GROUP BY?

DISTINCT is much faster with large amount data. I tested this, and found that on an indexed column, mysql, group by was about 6x slower than distinct with a fairly complicated query.

Can you use distinct twice in SQL?

No you can’t use that, it will throw an error, but there are other alternatives where you can get your desired results.

Which clause restricts which groups are displayed?

The WHERE clause restricts which rows are processed. The HAVING clause determines which groups are displayed in the query results.

Which clause is used to group matching values of a specified column together?

Introduction to SQL GROUP BY clause To group rows into groups, you use the GROUP BY clause. The GROUP BY clause is an optional clause of the SELECT statement that combines rows into groups based on matching values in specified columns. One row is returned for each group.

Can we use distinct and sum together in SQL?

4 Answers. Distinct is used to select distinct elements, nothing more, while you want to aggregate and for that you need GROUP BY and aggregation functions ( SUM ).

Can you sum distinct in SQL?

DISTINCT instructs the SUM() function to calculate the sum of the only distinct values. … expression is any valid expression that returns an exact or approximate numeric value. Note that aggregate functions or subqueries are not accepted in the expression.

How do you use distinct aggregate?

1. SELECT SUM (DISTINCT (ID)) AS ‘Sum of distinct values’, SUM (ID) AS ‘Sum of all values’, …
2. SELECT SUM (ID) AS ‘Sum of distinct values’ FROM (SELECT * …
3. SELECT AVG (DISTINCT (ID)) AS ‘AVG of distinct values’, AVG (ID) AS ‘AVG of all values’, …
4. SELECT COUNT (DISTINCT (ID)) AS ‘COUNT of distinct values’,