SQL | MCQs

Explanation

The operator that tests column for the absence of data is an is NULL operator. The NULL operator is used in the database for representing that a particular field is empty.

SELECT ‘column_name’

FROM ‘table_name’

WHERE ‘column_name’ IS NULL

Explanation

• The correct answer is: Dept_id should not be used in group by clause (although this is not the case in the given query, as it uses dept_name)
• The error in the statement is that the ID column is not included in the GROUP BY clause. When using an aggregate function like AVG, all non-aggregated columns in the SELECT clause must be included in the GROUP BY clause.

Explanation

• The HAVING clause is used in SQL to filter groups of rows based on a condition, similar to how the WHERE clause filters individual rows.
• The HAVING clause is applied after the GROUP BY clause, which groups the rows into sets, whereas the WHERE clause is applied before the GROUP BY clause.

Explanation

The SERIALIZABLE isolation level is the strictest transaction isolation level provided by SQL Server. It ensures that transactions are executed in a serialized manner, as if they were the only transaction operating on the database. This means that:

• No other transactions can modify data being read by a transaction.
• No other transactions can insert new data that would affect the results of a transaction.
• No other transactions can delete data that a transaction is using.

Explanation

Create Table By Entering Data. Design View. While Using Wizard.

Explanation

Explanation

SQLite Is the built-in database of Android.

SQLite Database is an open-source database provided in Android which is used to store data inside the user's device in the form of a Text file.

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 ND3-12-2022

Explanation

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