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  • [PostgreSQL] Ensure Uniqueness in Postgres

    Let’s say we have a bank. Our bank wants to give each account for each user a unique name, for instance, “Personal” or “Checking.” How can we make sure each account has a unique name for each user?

    Add unique constraint when create a new table:

    CREATE TABLE directors (
      id SERIAL PRIMARY KEY,
      name VARCHAR(100) UNIQUE NOT NULL    
    )

    Change existing table, modify one field to be unique:

    ALTER TABLE directors ADD CONSTRAINT directors_name_unique UNIQUE(name)

    So now if we trying to insert the duplicate rows it will report error:

    INSERT INTO directors (name) VALUES ('Quintin Tarantino'), ('Quintin Tarantino') ;

    Sometime, the unique constraint can be a combination of mulit fields:

    ALTER TABLE movies ADD CONSTRAINT unique_title_and_release UNIQUE(title, release-date)
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  • 原文地址:https://www.cnblogs.com/Answer1215/p/6925919.html
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