What is a self join in SQL Server?

What is a self join in SQL Server?

- It is a query in which two instances of the same table will be joined in the query.
- It is used to join a table to itself.

Syntax:
SELECT a.column_name, b.column_name, …
FROM table1 a, table1 b
WHERE a.commonfield = b.commomfield;

Example:
SELECT a.eId, b.eName, a.eSalary
FROM EMPLOYEE a, EMPLOYEE b
WHERE a. eSalary < b.Salary;
Sql server - Explain the various types of concurrency problem.
Types of concurrency problem:- Lost or buried updates: - When the same row is selected for updates by two or more transactions and updates the row based on the value originally selected.........
Sql server - Describe optimistic and pessimistic concurrency
Optimistic concurrency: - Assumes that a resource is likely to be available at all times. This means that resource locking is very unlikely......
Sql server - What are the differences between lost updates and uncommitted dependencies?
Lost updates results in loss of data. It is a write operation. Uncommitted dependency reads data that has not been committed yet........
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