Question: What Is Difference Between Unique And Distinct?

Can I use distinct in where clause?

Within the WHERE clause lies many possibilities for modifying your SQL statement.

Among these possibilities are the EXISTS, UNIQUE, DISTINCT, and OVERLAPS predicates.

Here are some examples of how to use these in your SQL statements..

Can we use distinct in group by?

SELECT DISTINCT can be used to give distinct values. Use it to remove duplicate records and it can be used with aggregate function as well. For example: MAX, AVG etc. … Select group by can be used to get data from different columns and group into one or more column.

Which is faster distinct or group by in Oracle?

SELECT DISTINCT will always be the same, or faster, than a GROUP BY. On some systems (i.e. Oracle), it might be optimized to be the same as DISTINCT for most queries. On others (such as SQL Server), it can be considerably faster. This isn’t always possible but when available you will see a faster response.

What is difference between count and distinct count?

2 Answers. Query select count(distinct a) will give you number of unique values in a. While query select distinct count(a) will give you list of unique counts of values in a. Without grouping it will be just one line with total count.

Is distinct or group by better?

While DISTINCT better explains intent, and GROUP BY is only required when aggregations are present, they are interchangeable in many cases. Same operators, same number of reads, negligible differences in CPU and total duration (they take turns “winning”).

What is a distinct value?

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.

Is distinct slow?

Very few queries may perform faster in SELECT DISTINCT mode, and very few will perform slower (but not significantly slower) in SELECT DISTINCT mode but for the later case it is likely that the application may need to examine the duplicate cases, which shifts the performance and complexity burden to the application.

What can be used instead of distinct in SQL?

You can use GROUP BY to select distinct values in SQL without using the DISTINCT keyword.

How do you retrieve unique rows from database without using distinct or unique keyword?

SQL | Remove Duplicates without DistinctRemove 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 = 1.2.Remove Duplicates using self Join. … Remove Duplicates using group By.

Does Count distinct count nulls?

COUNT(expression) like all aggregate functions, can take an optional DISTINCT clause. The DISTINCT clause counts only those columns having distinct (unique) values. COUNT DISTINCT does not count NULL as a distinct value. … The ALL keyword counts all non-NULL values, including all duplicates.

How do I count distinct rows in SQL?

Syntax. SELECT COUNT(DISTINCT column) FROM table; This statement would count all the unique entries of the attribute column in the table . DISTINCT ensures that repeated entries are only counted once.

How do I count the number of rows in SQL query?

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.

What is faster distinct or group by?

SELECT DISTINCT will always be the same, or faster, than a GROUP BY. On some systems (i.e. Oracle), it might be optimized to be the same as DISTINCT for most queries. On others (such as SQL Server), it can be considerably faster.

What is the difference between distinct and all in SQL?

The ALL, DISTINCT, and DISTINCTROW options specify whether duplicate rows should be returned. If none of these options are given, the default is ALL (all matching rows are returned). DISTINCT and DISTINCTROW are synonyms and specify removal of duplicate rows from the result set.

How do you use distinct?

SQL SELECT DISTINCT Statement SELECT DISTINCT returns only distinct (i.e. different) values. The DISTINCT keyword eliminates duplicate records from the results. DISTINCT can be used with aggregates: COUNT, AVG, MAX, etc. It operates on a single column.

What is distinct count in pivot table?

By default, a Pivot Table will count all records in a data set. To show a unique or distinct count in a pivot table, you must add data to the object model when the pivot table is created. In the example shown, the pivot table displays how many unique colors are sold in each state.

Does group by eliminate duplicates?

5 Answers. GROUP BY does not “remove duplicates”. GROUP BY allows for aggregation. If all you want is to combine duplicated rows, use SELECT DISTINCT.

Why distinct is bad 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. …