SQL Variables

What are SQL variables, and how are they used?

SQL variables are placeholders that hold data values. They are used to store intermediate results or values that need to be reused within a single SQL statement or block of statements. They enhance code readability and maintainability by avoiding repetition.

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Description

Example H2

Example H3

SQL variables are not like variables in programming languages like Python or Java. They are temporary storage locations within a specific SQL session. They are declared and assigned values within a particular block of SQL code, like a stored procedure or a batch of statements. They are not stored in the database itself, but rather exist only during the execution of the code. This makes them useful for calculations, loops, and conditional logic within a single transaction. They are particularly helpful for avoiding code duplication and improving readability. Variables can be used to store values from user input, results of queries, or intermediate calculations. This makes them a powerful tool for dynamic SQL statements.

Why SQL Variables is important

SQL variables improve code organization and efficiency by reducing redundancy. They allow for dynamic queries and conditional logic within a single SQL block, making the code more readable and maintainable. This is especially useful in stored procedures and complex data manipulation tasks.

SQL Variables Example Usage


-- Sample tables
CREATE TABLE Customers (
    CustomerID INT,
    Name VARCHAR(50)
);

CREATE TABLE Orders (
    OrderID INT,
    CustomerID INT
);

INSERT INTO Customers (CustomerID, Name) VALUES
(1, 'Alice'),
(2, 'Bob'),
(3, 'Charlie');

INSERT INTO Orders (OrderID, CustomerID) VALUES
(101, 1),
(102, 2),
(103, 1),
(104, 2);

-- Using UNION to get unique customer names and order IDs
SELECT Name FROM Customers
UNION
SELECT CustomerID FROM Orders;

-- Using UNION ALL to get all customer names and order IDs, including duplicates
SELECT Name FROM Customers
UNION ALL
SELECT CustomerID FROM Orders;

-- Clean up
DROP TABLE Customers;
DROP TABLE Orders;

SQL Variables Syntax

Common Mistakes

Forgetting to declare the variable before using it.
Using the wrong data type for the variable.
Trying to use a variable outside the scope where it was declared.
Incorrectly assigning a value to the variable.

Frequently Asked Questions (FAQs)

How are SQL variables different from variables in programming languages like Python or Java?

SQL variables live only for the duration of your current SQL session or the specific stored procedure that declares them. Unlike Python or Java variables, they are not persisted in memory between sessions, nor are they stored in the database. They serve as temporary placeholders for query results, user input, or intermediate calculations inside a single transaction or batch of statements.

What are the most common use cases for session-scoped SQL variables?

Session variables are ideal for on-the-fly calculations, loop counters, conditional branching, and passing values between multiple SELECT, UPDATE, or INSERT statements in the same batch. Because they eliminate repeated subqueries and improve readability, they are a powerful way to build dynamic SQL, parameterize stored procedures, and avoid hard-coding values.

How can a modern SQL editor like Galaxy make working with SQL variables easier?

Galaxy’s context-aware AI copilot autocompletes variable names, flags scope issues, and even rewrites dynamic SQL when your schema changes. Its reimagined parameterization workflow lets you declare, edit, and test variables in a single pane—speeding up debugging and reducing errors. With built-in sharing and endorsement features, your entire team can reuse well-tested variable-driven queries instead of pasting snippets in Slack or Notion.