What is UNION in SQL injection?

Union based SQL injection allows an attacker to extract information from the database by extending the results returned by the original query. The Union operator can only be used if the original/new queries have the same structure (number and data type of columns). Description.

What is UNION attack?

When an application is vulnerable to SQL injection and the results of the query are returned within the application’s responses, the UNION keyword can be used to retrieve data from other tables within the database. This results in an SQL injection UNION attack.

How does UNION all work in SQL?

The SQL UNION ALL operator is used to combine the result sets of 2 or more SELECT statements. It does not remove duplicate rows between the various SELECT statements (all rows are returned). Each SELECT statement within the UNION ALL must have the same number of fields in the result sets with similar data types.

How do you do a UNION in SQL?

SQL UNION Operator

  1. Every SELECT statement within UNION must have the same number of columns.
  2. The columns must also have similar data types.
  3. The columns in every SELECT statement must also be in the same order.

What is difference UNION and UNION all in SQL?

The only difference between Union and Union All is that Union extracts the rows that are being specified in the query while Union All extracts all the rows including the duplicates (repeated values) from both the queries.

Where can I find SQL injection?

The most common other locations where SQL injection arises are:

  • In UPDATE statements, within the updated values or the WHERE clause.
  • In INSERT statements, within the inserted values.
  • In SELECT statements, within the table or column name.
  • In SELECT statements, within the ORDER BY clause.

Why UNION is used in SQL query?

What Is UNION in SQL? The UNION operator is used to combine the data from the result of two or more SELECT command queries into a single distinct result set. This operator removes any duplicates present in the results being combined.

What is difference between UNION and UNION all in SQL Server?

The UNION ALL command is equal to the UNION command, except that UNION ALL selects all values. The difference between Union and Union all is that Union all will not eliminate duplicate rows, instead it just pulls all rows from all tables fitting your query specifics and combines them into a table.