GROUP BY lets you use aggregate functions, like AVG, MAX, MIN, SUM, and COUNT. On the other hand DISTINCT just removes duplicates. For example, if you have a bunch of purchase records, and you want to know how much was spent by each department, you might do something like: SELECT department, SUM (amount) FROM purchases GROUP BY department
What is difference between distinct and group by in SQL?
What is difference between DISTINCT and GROUP BY? 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.
When does group by give the same result as of distinct?
The group by gives the same result as of distinct when no aggregate function is present. The SQL Server query optimizer produces the same plan for both the queries as shown below.
What is the difference between group by and distinct in Salesforce?
GROUP BY lets you use aggregate functions, like AVG, MAX, MIN, SUM, and COUNT. On the other hand DISTINCT just removes duplicates. For example, if you have a bunch of purchase records, and you want to know how much was spent by each department, you might do something like: SELECT department, SUM (amount) FROM purchases GROUP BY department
Does group by and distinct work similarly for Unique Records?
A lot of developers think that Group by and distinct works similarly when it comes to getting unique records. and they assume that the performance remains the same in both of the cases. But this is not the case. In some cases, Group by and distinct behave similarly but not in every case.
Is GROUP BY and distinct the same?
When and where to use GROUP BY and DISTINCT. 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.
What is the functional difference between distinct and GROUP BY?
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.
What is a distinct group?
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 functional difference is thus obvious. The group by can also be used to find distinct values as shown in below query.
Which is better distinct or GROUP BY in Oracle?
DISTINCT implies you want a distinct set of columns. However, GROUP BY implies you want to compute some sort of aggregate value which you are not.
Why GROUP BY is faster than distinct?
DISTINCT would usually be faster than GROUP BY if a) there's no index on that column and b) you are not ordering as well since GROUP BY does both filtering and ordering.
What is difference between GROUP BY and order by?
Key Differences between GROUP BY and ORDER 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.
Is GROUP BY or distinct faster?
The GROUP BY clause is faster than the SELECT DISTINCT clause (at least in these tests) because it does not require writing to a temporary file on disk.
What do you mean by distinct?
Definition of distinct 1 : distinguishable to the eye or mind as being discrete (see discrete sense 1) or not the same : separate a distinct cultural group teaching as distinct from research. 2 : presenting a clear unmistakable impression a neat distinct handwriting. 3 archaic : notably decorated.
What is GROUP BY in SQL?
The SQL GROUP BY Statement The GROUP BY statement groups rows that have the same values into summary rows, like "find the number of customers in each country". The GROUP BY statement is often used with aggregate functions ( COUNT() , MAX() , MIN() , SUM() , AVG() ) to group the result-set by one or more columns.
Which is faster GROUP BY or distinct 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.
Is distinct faster than Row_number?
In my experience, an aggregate (DISTINCT or GROUP BY) can be quicker then a ROW_NUMBER() approach. Saying that, ROW_NUMBER is better with SQL Server 2008 than SQL Server 2005. However, you'll have to try for your situation.
Does distinct affect performance?
Yes, the application needs to compare every record to the "distinct" records cache as it goes. You can improve performance by using an index, particularly on the numeric and date fields. The operation you describe is O(n²).
Can we use group by without where clause?
A) Using PostgreSQL GROUP BY without an aggregate function example. You can use the GROUP BY clause without applying an aggregate function. In this case, the GROUP BY works like the DISTINCT clause that removes duplicate rows from the result set.
How do I count rows in SQL?
Counting all of the Rows in a Table. To counts all of the rows in a table, whether they contain NULL values or not, use COUNT (*). That form of the COUNT () function basically returns the number of rows in a result set returned by a SELECT statement.
Can distinct be used on multiple columns?
DISTINCT can be also used on multiple columns at once; in that case it will evaluate the duplicates based on the combination of values of those columns. DISTINCT behavior can be simulated by GROUP BY clause.
Why we should not use distinct in SQL?
The fact that the resultset has duplicates is frequently (though not always) the result of a poor database design, an ineffective query, or both. In any case, issuing the query without the DISTINCT keyword yields more rows than expected or needed so the keyword is employed to limit what is returned to the user.
What is the difference between distinct and unique?
As adjectives the difference between distinct and unique is that distinct is capable of being perceived very clearly while unique is (not comparable) being the only one of its kind; unequaled, unparalleled or unmatched.
Which SQL statement is used to return only different values?
The SQL SELECT DISTINCT Statement The SELECT DISTINCT statement is used to return only distinct (different) values. Inside a table, a column often contains many duplicate values; and sometimes you only want to list the different (distinct) values.
How use distinct and count in SQL query?
SQL SELECT DISTINCT Statement SELECT DISTINCT returns only distinct (different) values. SELECT DISTINCT eliminates duplicate records from the results. DISTINCT can be used with aggregates: COUNT, AVG, MAX, etc. DISTINCT operates on a single column. DISTINCT for multiple columns is not supported.
What's the difference from a mere duplicate removal functionality point of view
Apart from the fact that unlike DISTINCT, GROUP BY allows for aggregating data per group (which has been mentioned by many other answers), the most important difference in my opinion is the fact that the two operations "happen" at two very different steps in the logical order of operations that are executed in a SELECT statement.
1. It doesn't depend on the projection
An example where not depending on the projection is useful is if you want to calculate window function s on distinct values:
2. It cannot use any values from the projection
One of SQL's drawbacks is its verbosity at times. For the same reason as what we've seen before (namely the logical order of operations), we cannot "easily" group by something we're projecting.
