ON Clause can
be used to join columns that have different names
. We use ON clause to specify a join condition. This lets us specify join conditions separate from any search or filter conditions in the WHERE clause.
What is the difference between the on and WHERE clauses?
Is there a difference between the WHERE and ON clause? Yes.
ON should be used to define the join condition and WHERE should be used to filter the data
.
What is clause in SQL with example?
Clauses help us filter and analyze data quickly. When we have large amounts of data stored in the database, we use Clauses to query and get data required by the user. Some of the examples of clauses are –
where, and, or, like, top, etc
.
What is on in join?
The ON
clause defines the relationship between the tables
. The WHERE clause describes which rows you are interested in. Many times you can swap them and still get the same result, however this is not always the case with a left outer join.
What is have clause in SQL?
A HAVING clause in SQL
specifies that an SQL SELECT statement must only return rows where aggregate values meet the specified conditions
. … To view the present condition formed by the GROUP BY clause, the HAVING clause is used.
Can we use joins in WHERE clause?
To use the WHERE clause to perform the same join as you perform using the
INNER JOIN
syntax, enter both the join condition and the additional selection condition in the WHERE clause. The tables to be joined are listed in the FROM clause, separated by commas. This query returns the same output as the previous example.
Is inner join same as WHERE clause?
INNER JOIN is
ANSI syntax
whereas the WHERE syntax is more relational model oriented. The INNER JOIN is generally considered more readable and it is a cartesian product of the tables, especially when you join lots of tables but the result of two tables JOIN’ed can be filtered on matching columns using the WHERE clause.
What triggers SQL?
A SQL trigger is
a database object which fires when an event occurs in a database
. We can execute a SQL query that will “do something” in a database when a change occurs on a database table such as a record is inserted or updated or deleted. For example, a trigger can be set on a record insert in a database table.
What is difference between WHERE and HAVING clause in SQL?
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 1 1 in SQL?
The 1=1 is ignored by always all rdbms. There is no tradeoff executing a query with WHERE 1=1.
Building dynamic WHERE conditions
, like ORM frameworks or other do very often, it is easier to append the real where conditions because you avoid checking for prepending an AND to the current condition.
When on is used in SQL?
The ON Clause makes code easy to understand. ON Clause can be
used to join columns that have different names
. We use ON clause to specify a join condition. This lets us specify join conditions separate from any search or filter conditions in the WHERE clause.
How can I merge two tables in SQL query?
- use the keyword UNION to stack datasets without duplicate values.
- use the keyword UNION ALL to stack datasets with duplicate values.
- use the keyword INNER JOIN to join two tables together and only get the overlapping values.
What is a full join?
A FULL JOIN
returns all the rows from the joined tables
, whether they are matched or not i.e. you can say a full join combines the functions of a LEFT JOIN and a RIGHT JOIN . Full join is a type of outer join that’s why it is also referred as full outer join.
Which is faster WHERE or HAVING?
Solution: The theory (by theory I mean SQL Standard) says that
WHERE restricts the result set before returning
rows and HAVING restricts the result set after bringing all the rows. So WHERE is faster.
How do I count 1 in SQL?
- SELECT user_id ,COUNT(*) count.
- FROM PAYMENT.
- GROUP BY account,user_id ,date.
- Having COUNT(*) > 1.
What is difference between truncate and delete command?
Key differences between DELETE and TRUNCATE
The DELETE statement is used when we want to remove some or all of the records from the table, while the TRUNCATE statement
will delete entire rows
from a table. DELETE is a DML command as it only modifies the table data, whereas the TRUNCATE is a DDL command.
