Question: What Is The Difference Between The Where And Having Clauses In SQL Statements?

What is the difference between the where and having SQL clauses?

WHERE Clause is used to filter the records from the table based on the specified condition.

HAVING Clause is used to filter record from the groups based on the specified condition..

What is the use of having clause in SQL?

The HAVING clause specifies a search condition for a group. You often use the HAVING clause with the GROUP BY clause. The GROUP BY clause groups a set of rows into a set of summary rows or groups. Then the HAVING clause filters groups based on a specified condition.

How do you count in SQL?

SQL COUNT() FunctionSQL COUNT(column_name) Syntax. The COUNT(column_name) function returns the number of values (NULL values will not be counted) of the specified column: … SQL COUNT(*) Syntax. The COUNT(*) function returns the number of records in a table: … SQL COUNT(DISTINCT column_name) Syntax.

How can I make SQL query run faster?

10 More Do’s and Don’ts for Faster SQL QueriesDo use temp tables to improve cursor performance. … Don’t nest views. … Do use table-valued functions. … Do use partitioning to avoid large data moves. … If you must use ORMs, use stored procedures. … Don’t do large ops on many tables in the same batch. … Don’t use triggers. … Don’t cluster on GUID.More items…•

Why group by is used 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.

What is group by and having in SQL?

Summary. The GROUP BY Clause is used to group rows with same values . The GROUP BY Clause is used together with the SQL SELECT statement. … The HAVING clause is used to restrict the results returned by the GROUP BY clause.

Is like in SQL?

The SQL LIKE Operator The LIKE operator is used in a WHERE clause to search for a specified pattern in a column. There are two wildcards often used in conjunction with the LIKE operator: % – The percent sign represents zero, one, or multiple characters. _ – The underscore represents a single character.

How do you delete duplicate rows in SQL?

Delete Duplicates From a Table in SQL ServerFind duplicate rows using GROUP BY clause or ROW_NUMBER() function.Use DELETE statement to remove the duplicate rows.

Where and having clauses Cannot be used together in a SQL statement?

WHERE and HAVING clauses cannot be used together in a SQL statement. The HAVING clause conditions can have aggregate functions. The HAVING clause conditions can use aliases for the columns. The WHERE clause is used to exclude rows before the grouping of data.

Which is faster where or having?

Both the statements will be having same performance as SQL Server is smart enough to parse both the same statements into a similar plan. So, it does not matter if you use WHERE or HAVING in your query. … “WHERE” is faster than “HAVING”!

Are joins faster than where clauses?

10 Answers. Theoretically, no, it shouldn’t be any faster. The query optimizer should be able to generate an identical execution plan. However, some database engines can produce better execution plans for one of them (not likely to happen for such a simple query but for complex enough ones).

Which SQL function is used to count the number of rows in SQL query?

The SQL COUNT(), AVG() and SUM() Functions The COUNT() function returns the number of rows that matches a specified criterion. The AVG() function returns the average value of a numeric column. The SUM() function returns the total sum of a numeric column.

Where does having go in SQL?

SQL HAVING Clause The HAVING clause is like WHERE but operates on grouped records returned by a GROUP BY. HAVING applies to summarized group records, whereas WHERE applies to individual records. Only the groups that meet the HAVING criteria will be returned.

Can having be used without group by?

1) Let HC be the having clause. Let TE be the table expression that immediately contains HC. If TE does not immediately contain a group by clause, then “GROUP BY ()” is implicit.

Can you have a where and having in the same statement?

A query can contain both a WHERE clause and a HAVING clause. … The HAVING clause is then applied to the rows in the result set. Only the groups that meet the HAVING conditions appear in the query output. You can apply a HAVING clause only to columns that also appear in the GROUP BY clause or in an aggregate function.

How use multiple orders in SQL?

If you specify multiple columns, the result set is sorted by the first column and then that sorted result set is sorted by the second column, and so on. The columns that appear in the ORDER BY clause must correspond to either column in the select list or to columns defined in the table specified in the FROM clause.

Which join is faster in SQL?

It’s because SQL Server wants to do a hash match for the INNER JOIN , but does nested loops for the LEFT JOIN ; the former is normally much faster, but since the number of rows is so tiny and there’s no index to use, the hashing operation turns out to be the most expensive part of the query.

How do I select duplicate rows in SQL?

To select duplicate values, you need to create groups of rows with the same values and then select the groups with counts greater than one. You can achieve that by using GROUP BY and a HAVING clause.

Which one sorts rows in SQL?

The SQL ORDER BY Keyword The ORDER BY keyword is used to sort the result-set in ascending or descending order. The ORDER BY keyword sorts the records in ascending order by default. To sort the records in descending order, use the DESC keyword.

How do you order two things in SQL?

After the ORDER BY keyword, add the name of the column by which you’d like to sort records first (in our example, salary). Then, after a comma, add the second column (in our example, last_name ). You can modify the sorting order (ascending or descending) separately for each column.

Can I use count in where clause?

The HAVING clause with SQL COUNT() function can be used to set a condition with the select statement. The HAVING clause is used instead of WHERE clause with SQL COUNT() function.