SQL: DISTINCT Clause
- Description. The SQL DISTINCT clause is used to remove duplicates from the result set of a SELECT statement.
- Syntax. The columns or calculations that you wish to retrieve. ...
- Note. ...
- DDL/DML for Examples. ...
- Example - Finding Unique Values in a Column. ...
- Example - Finding Unique Values in Multiple Columns. ...
- Example - How the DISTINCT Clause handles NULL Values. ...
How do you select distinct in SQL?
Dec 09, 2016 · SQL | Distinct Clause. The distinct keyword is used in conjunction with select keyword. It is helpful when there is a need of avoiding duplicate values present in any specific columns/table. When we use distinct keyword only the unique values are fetched.
What are different clauses in SQL?
The SQL DISTINCT clause is used to remove duplicates from the result set of a SELECT statement. Syntax The syntax for the DISTINCT clause in SQL is: SELECT DISTINCT expressions FROM tables [WHERE conditions]; Parameters or Arguments expressions The columns or calculations that you wish to retrieve. tables
How to use distinct in SQL?
The DISTINCT clause is used in the SELECT statement to filter out duplicate rows in the result set. You can use DISTINCT when you select a single column, or when you select multiple columns as we did in our example.
What does SQL SELECT DISTINCT mean?
SQL DISTINCT clause is used to remove the duplicates columns from the result set. The distinct keyword is used with select keyword in conjunction. It is helpful when we avoid duplicate values present in the specific columns/tables. The unique values are fetched when we use the distinct keyword. SELECT DISTINCT returns only distinct ( different) values.
Is it good to use distinct in SQL?
The distinct keyword is used in conjunction with select keyword. It is helpful when there is a need of avoiding duplicate values present in any specific columns/table.Sep 11, 2020
What is distinct function explain with example?
The distinct keyword is used with SELECT statement to retrieve unique values from the table. Distinct removes all the duplicate records while retrieving records from any table in the database.
What is the use of distinct in MySQL explain with example?
We can use the MySQL DISTINCT clause to return a single field that removes the duplicates from the result set. For example: SELECT DISTINCT state FROM customers; This MySQL DISTINCT example would return all unique state values from the customers table.
Where does distinct go in SQL?
Note that the DISTINCT keyword must be placed before the columns you specify. You can specify more than one column to be DISTINCT , which will make SQL return only unique combinations of those columns' values.Apr 23, 2021
What is the difference between unique and distinct in SQL?
Unique and Distinct are two SQL constraints. The main difference between Unique and Distinct in SQL is that Unique helps to ensure that all the values in a column are different while Distinct helps to remove all the duplicate records when retrieving the records from a table.Jul 2, 2019
Can we use multiple distinct in SQL?
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.Jul 28, 2018
Is using distinct in SQL bad?
So, is SQL DISTINCT good or bad in removing duplicates in results? The results say that it's good. It's not better or worse than GROUP BY because the plans are the same. But it's a good habit to check the execution plan.Sep 6, 2021
Does distinct apply to all columns?
Yes, DISTINCT works on all combinations of column values for all columns in the SELECT clause.Sep 1, 2006
Can Unique Key have NULL values?
Details. You can insert NULL values into columns with the UNIQUE constraint because NULL is the absence of a value, so it is never equal to other NULL values and not considered a duplicate value. This means that it's possible to insert rows that appear to be duplicates if one of the values is NULL .
Can we use unique 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.Jan 14, 2022
What is the use of distinct function?
The Distinct function evaluates a formula across each record of a table and returns a one-column table of the results with duplicate values removed.Feb 15, 2022
Why does distinct have to be first?
DISTINCT means "eliminate duplicate rows". It doesn't make sense at the column level. This is why it stays between SELECT and the list of selected expressions. To answer the question in title: because the documentation of SELECT says so.Apr 3, 2017
Does distinct have to be first SQL?
Get Your SQL Cheat Sheet Perhaps the user is trying to show unique values of a particular column. Because the DISTINCT keyword applies to the entire result set, and not just one column, the DISTINCT must go at the start of the query, just after SELECT: SELECT DISTINCT col1, col2, col3 FROM table…
Description
The SQL DISTINCT clause is used to remove duplicates from the result set of a SELECT statement.
Example - Finding Unique Values in a Column
Let's look at how to use the DISTINCT clause to find the unique values within one column in a table.
Example - Finding Unique Values in Multiple Columns
Next, let's look at how to use the SQL DISTINCT clause to remove duplicates from more than one field in a SELECT statement.
Example - How the DISTINCT Clause handles NULL Values
Finally, does the DISTINCT clause consider NULL to be a unique value in SQL? The answer is yes. Let's explore this further.
Parameters
Expressions: The columns or calculations that we want to retrieve are called expression.
Example: Finding Unique Values in the Column
Look at the DISTINCT clause to find the unique values within one column in the table.
Example: Finding Unique Values in Multiple Column
The SQL DISTINCT clause is used to remove the duplicate records from many fields in the SELECT statement.
Example: DISTINCT Clause handles NULL Values
The DISTINCT clause considers NULL to the unique value in SQL. We have a table called products which contains the below data.
How do we use distinct statement what is its use?
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.
What is the most common type of join?
SQL INNER JOIN (simple join) It is the most common type of SQL join. SQL INNER JOINS return all rows from multiple tables where the join condition is met.
How does distinct keyword work?
Introduction to SQL Server SELECT DISTINCT clause The query returns only distinct values in the specified column. In other words, it removes the duplicate values in the column from the result set. In other words, the DISTINCT clause treats all NULL “values” as the same value.
What is the difference between unique and distinct?
Unique and Distinct are two SQL constraints. The main difference between Unique and Distinct in SQL is that Unique helps to ensure that all the values in a column are different while Distinct helps to remove all the duplicate records when retrieving the records from a table.
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 we use distinct multiple columns?
The DISTINCT clause keeps one row for each group of duplicates. The DISTINCT clause can be used on one or more columns of a table. If you specify multiple columns, the DISTINCT clause will evaluate the duplicate based on the combination of values of these columns.
What is not like SQL?
The NOT LIKE operator in SQL is used on a column which is of type varchar . Usually, it is used with % which is used to represent any string value, including the null character . The string we pass on to this operator is not case-sensitive.
Syntax
The basic syntax of DISTINCT keyword to eliminate the duplicate records is as follows −
Example
First, let us see how the following SELECT query returns the duplicate salary records.
