- Why having clause is used in SQL?
- Can you have multiple where clauses in SQL?
- Where we can use having clause in SQL?
- What is the difference between where and having clauses?
- Can we use having and where clause together?
- Which is faster where or having?
- Which SQL keyword is used to retrieve maximum value?
- Was having is correct?
- How do I quickly query in SQL?
- Which join is faster in SQL?
- How do I select duplicate rows in SQL?
- How do you do multiple or condition in SQL?
- What is the difference between the where and having clauses in SQL statements?
- Which is faster joins or subqueries?
- Can I use count in where clause?
- Why use subqueries instead of joins?
- Why use instead of join?
- Can we use JOIN IN subquery?
- How can I speed up SQL query?
- What is the difference between truncate and delete?
- Can you have 2 select statements in SQL?
Why having clause is used 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..
Can you have multiple where clauses in SQL?
You can specify multiple conditions in a single WHERE clause to, say, retrieve rows based on the values in multiple columns. You can use the AND and OR operators to combine two or more conditions into a compound condition. AND, OR, and a third operator, NOT, are logical operators.
Where we can use having clause in SQL?
The SQL HAVING clause is used in combination with the GROUP BY clause to restrict the groups of returned rows to only those whose the condition is TRUE.
What is the difference between where and having 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.
Can we use having and where clause together?
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.
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”!
Which SQL keyword is used to retrieve maximum value?
MAXMAX() is the SQL keyword is used to retrieve the maximum value in the selected column.
Was having is correct?
You don’t use the word have as a main verb in the progressive to talk about things you own or possess. So the correct sentence is: … However, you can use it in the progressive if you talk about actions, events, or activities as follows: He’s having a chat with Joan.
How do I quickly query in SQL?
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…•
Which join is faster in SQL?
Well, in general INNER JOIN will be faster because it only returns the rows matched in all joined tables based on the joined column. But LEFT JOIN will return all rows from a table specified LEFT and all matching rows from a table specified RIGHT.
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.
How do you do multiple or condition in SQL?
The SQL AND condition and OR condition can be combined to test for multiple conditions in a SELECT, INSERT, UPDATE, or DELETE statement. When combining these conditions, it is important to use parentheses so that the database knows what order to evaluate each condition.
What is the difference between the where and having clauses in SQL statements?
The main difference between WHERE and HAVING clause comes when used together with GROUP BY clause, In that case WHERE is used to filter rows before grouping and HAVING is used to exclude records after grouping. This is the most important difference and if you remember this, it will help you write better SQL queries.
Which is faster joins or subqueries?
The advantage of a join includes that it executes faster. The retrieval time of the query using joins almost always will be faster than that of a subquery. By using joins, you can maximize the calculation burden on the database i.e., instead of multiple queries using one join query.
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.
Why use subqueries instead of joins?
Subqueries can be used to return either a scalar (single) value or a row set; whereas, joins are used to return rows. A common use for a subquery may be to calculate a summary value for use in a query. For instance we can use a subquery to help us obtain all products have a greater than average product price.
Why use instead of join?
Actually you often need both “WHERE” and “JOIN”. “JOIN” is used to retrieve data from two tables – based ON the values of a common column. If you then want to further filter this result, use the WHERE clause. For example, “LEFT JOIN” retrieves ALL rows from the left table, plus the matching rows from the right table.
Can we use JOIN IN subquery?
A subquery can be used with JOIN operation. … The temporary table from the subquery is given an alias so that we can refer to it in the outer select statement. Note that the left and right table of the join keyword must both return a common key that can be used for the join.
How can I speed up SQL query?
10 Ways to Improve SQL Query PerformanceAvoid Multiple Joins in a Single Query. … Eliminate Cursors from the Query. … Avoid Use of Non-correlated Scalar Sub Query. … Avoid Multi-statement Table Valued Functions (TVFs) … Creation and Use of Indexes. … Understand the Data. … Create a Highly Selective Index. … Position a Column in an Index.More items…•
What is the difference between truncate and delete?
Delete and truncate both commands can be used to delete data of the table. Delete is a DML command whereas truncate is DDL command. Truncate can be used to delete the entire data of the table without maintaining the integrity of the table. On the other hand , delete statement can be used for deleting the specific data.
Can you have 2 select statements in SQL?
The SQL UNION ALL operator is used to combine the result sets of 2 or more SELECT statements. It does not remove duplicate rows between the various SELECT statements (all rows are returned). Each SELECT statement within the UNION ALL must have the same number of fields in the result sets with similar data types.