Unique values in SQL are values that are distinct within a column. Ensuring uniqueness is crucial for data integrity. SQL provides various ways to identify and enforce this.
Unique values are essential in databases to avoid redundancy and maintain data accuracy. In a table, a column containing unique values ensures that no two rows have the same value in that specific column. This is vital for representing distinct entities or attributes. For example, in a customer table, the customer ID column should ideally contain unique values to identify each customer uniquely. SQL offers several methods to identify and enforce uniqueness. One common way is using the `DISTINCT` keyword in `SELECT` statements to retrieve only unique values. Another approach involves creating a unique constraint on a column to prevent the insertion of duplicate values during data entry. This constraint is enforced by the database system, ensuring data integrity. Understanding unique values is fundamental for building robust and reliable database applications.
Unique values are critical for data integrity and consistency. They prevent data duplication, enabling accurate analysis and reporting. They also simplify data management and reduce the risk of errors.
Unique values prevent two customers from sharing the same identifier, eliminating data redundancy and confusion during joins, updates, or deletes. In SQL you usually create a PRIMARY KEY or UNIQUE constraint on the customer_id column. The database engine then rejects any INSERT or UPDATE that would duplicate an existing value, preserving data integrity automatically.
SELECT DISTINCT and creating a UNIQUE constraint to handle duplicates?SELECT DISTINCT removes duplicates only in the query result set—your underlying table can still contain duplicate rows. A UNIQUE constraint (or PRIMARY KEY) lives at the schema level and blocks future duplicates from ever being stored. Think of DISTINCT as a diagnostic tool, and a UNIQUE constraint as a preventative guardrail.
Galaxy’s context-aware AI copilot can auto-generate SELECT DISTINCT queries, suggest appropriate UNIQUE constraints based on table metadata, and highlight duplicate rows in real time. With built-in sharing and endorsement features, your team can agree on the “single source of truth” queries for uniqueness checks without pasting SQL snippets in Slack. Try Galaxy for free at getgalaxy.io.
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