Imagine you want to clean up your database and decide to delete all records from the review table that have an id of 100 or less. what does your sql statement look like?

The query to delete rows for the given scenario is  

DELETE

FROM Review

WHERE Id < 100 OR Id = 100;

Explanation:

In SQL, the table can be removed using either DROP, TRUNCATE or DELETE commands.

DROP command is used to delete the whole structure of the table. The general syntax is given below.

DROP TABLE table_name;

After this command, the whole structure of the specified table will be deleted. This table will have to be created again in order to use it and put data in this table.

SELECT *

FROM table_name;

This command when executed after the DROP command, will show an error.

This command can be used to drop database objects like constraints, index and the others.

The TRUNCATE command removes all the rows from a table. The structure of the table remains intact and data can be put again in this table.

This command only removes the data currently present in the table.

The general syntax is given below.

TRUNCATE TABLE table_name;

The command below will compile but it will not return any rows.

SELECT *

FROM table_name;

Alternatively, DELETE keyword is used to drop only the rows from a given table.

The general syntax for deleting rows from a table is given below.

DELETE

FROM table_name

WHERE [condition];

The WHERE clause is optional in a DELETE query.

SELECT *

FROM table_name;

The above command will compile and return rows if rows are present in the table other than the deleted rows.

The table used in the given query is Review table. We assume that Id is the primary key for the Review table. The query becomes

DELETE

FROM Review;

The condition for this deletion is that Id should be less than or equal to 100. The final query is written as

DELETE

FROM Review

WHERE Id < 100 OR Id = 100;

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