Durability: This property ensures that the committed transactions are stored permanently in the database. Phantom reads: This occurs when two same queries when executed separately return different rows. For example, if transaction A retrieves some set of rows matching search criteria. Assume another transaction B retrieves new rows in addition to the rows obtained earlier for the same search criteria. The results are different. A table is an organized collection of data stored in the form of rows and columns. Columns can be categorized as vertical and rows as horizontal. The columns in a table are called fields while the rows can be referred to as records. 7. What are Constraints in SQL?

SQL standards state that the following three phenomena should be prevented whilst concurrent transactions. SQL standards define 4 levels of transaction isolations to deal with these phenomena.

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Constraints are used to specify the rules concerning data in the table. It can be applied for single or multiple fields in an SQL table during the creation of the table or after creating using the ALTER TABLE command. The constraints are: Dirty reads: If a transaction reads data that is written due to concurrent uncommitted transaction, these reads are called dirty reads. An alias is represented explicitly by the AS keyword but in some cases, the same can be performed without it as well. Nevertheless, using the AS keyword is always a good practice. SELECT A.emp_name AS "Employee" /* Alias using AS keyword */ where Salary not in (Select max(Salary) from Worker); Q-37. Write an SQL query to show one row twice in the results from a table.

The required query is: Select distinct length(DEPARTMENT) from Worker; Q-9. Write an SQL query to print the FIRST_NAME from the Worker table after replacing ‘a’ with ‘A’.The required query is: Select * from Worker where year(JOINING_DATE) = 2021 and month(JOINING_DATE) = 2; Q-21. Write an SQL query to fetch the count of employees working in the department ‘Admin’.