How to use variable in SQL query?

In SQL, variables are used to store data that can be used and manipulated throughout a program. They are essential for dynamic SQL queries, where the values of the variables can be determined at runtime.

The syntax for declaring and using variables is different in different SQL databases.

Here are some examples:

MySQL variable in SQL query

In MySQL, you can declare a variable using the SET or SELECT statement.

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SQL Server variable in SQL query

In SQL Server, you can declare a variable using the DECLARE statement and set its value using the SET statement.

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Oracle variable in SQL query

In Oracle, you can declare a variable in a PL/SQL block.

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PostgreSQL variable in SQL query

In PostgreSQL, you can use variables in functions, and the syntax is similar to Oracle's PL/SQL.

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In all cases, once a variable is declared and assigned a value, it can be used in a query like this:

or

Remember to check the documentation of the SQL database you are using for the exact syntax and usage of variables.

Conclusion

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