{"id":514,"date":"2026-06-10T04:04:29","date_gmt":"2026-06-10T04:04:29","guid":{"rendered":"https:\/\/mitalgoswami.in\/?p=514"},"modified":"2026-06-17T03:11:11","modified_gmt":"2026-06-17T03:11:11","slug":"integrity-constraints","status":"publish","type":"post","link":"https:\/\/mitalgoswami.in\/?p=514","title":{"rendered":"Integrity Constraints"},"content":{"rendered":"\n

The constraints you listed are Integrity Constraints<\/strong> in DBMS\/RDBMS. They help maintain the accuracy and consistency of data.<\/p>\n\n\n\n

1. NOT NULL Constraint<\/h3>\n\n\n\n

Ensures that a column cannot have a NULL (empty) value.<\/p>\n\n\n\n

Example:<\/strong><\/p>\n\n\n\n

CREATE TABLE Student (
    StudentID INT,
    Name VARCHAR(50) NOT NULL
);<\/code><\/pre>\n\n\n\n
Here, the Name<\/code> column must contain a value.<\/p>\n\n\n\n
\n\n\n\n
2. UNIQUE Constraint<\/h3>\n\n\n\n
Ensures that all values in a column are unique.<\/p>\n\n\n\n
Example:<\/strong><\/p>\n\n\n\n
CREATE TABLE Student (
    StudentID INT,
    Email VARCHAR(100) UNIQUE
);<\/code><\/pre>\n\n\n\n
No two students can have the same email address.<\/p>\n\n\n\n
\n\n\n\n
3. PRIMARY KEY Constraint<\/h3>\n\n\n\n
Uniquely identifies each record in a table.<\/p>\n\n\n\n
Properties:<\/strong><\/p>\n\n\n\n
    \n
  • Must be unique<\/li>\n\n\n\n
  • Cannot be NULL<\/li>\n\n\n\n
  • Only one primary key per table<\/li>\n<\/ul>\n\n\n\n
    Example:<\/strong><\/p>\n\n\n\n
    CREATE TABLE Student (
        StudentID INT PRIMARY KEY,
        Name VARCHAR(50)
    );<\/code><\/pre>\n\n\n\n
    StudentID<\/code> uniquely identifies each student.<\/p>\n\n\n\n
    \n\n\n\n
    4. FOREIGN KEY Constraint<\/h3>\n\n\n\n
    Establishes a relationship between two tables.<\/p>\n\n\n\n
    Example:<\/strong><\/p>\n\n\n\n
    Student Table<\/strong><\/p>\n\n\n\n
    CREATE TABLE Student (
        StudentID INT PRIMARY KEY,
        Name VARCHAR(50)
    );<\/code><\/pre>\n\n\n\n
    Course Table<\/strong><\/p>\n\n\n\n
    CREATE TABLE Course (
        CourseID INT PRIMARY KEY,
        StudentID INT,
        FOREIGN KEY (StudentID)
        REFERENCES Student(StudentID)
    );<\/code><\/pre>\n\n\n\n
    Here, StudentID<\/code> in the Course<\/code> table refers to StudentID<\/code> in the Student<\/code> table.<\/p>\n\n\n\n
    \n\n\n\n
    Summary Table<\/h2>\n\n\n\n
    Constraint<\/th>Purpose<\/th><\/tr><\/thead>
    NOT NULL<\/td>Prevents NULL values in a column<\/td><\/tr>
    UNIQUE<\/td>Ensures all values are different<\/td><\/tr>
    PRIMARY KEY<\/td>Uniquely identifies each row<\/td><\/tr>
    FOREIGN KEY<\/td>Maintains relationship between tables<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
    Example Combined<\/h3>\n\n\n\n
    CREATE TABLE Student (
        StudentID INT PRIMARY KEY,
        Name VARCHAR(50) NOT NULL,
        Email VARCHAR(100) UNIQUE
    );

    CREATE TABLE Result (
        ResultID INT PRIMARY KEY,
        StudentID INT,
        Marks INT,
        FOREIGN KEY (StudentID)
        REFERENCES Student(StudentID)
    );<\/code><\/pre>\n\n\n\n
    In this example:<\/p>\n\n\n\n
      \n
    • StudentID<\/code> \u2192 PRIMARY KEY<\/li>\n\n\n\n
    • Name<\/code> \u2192 NOT NULL<\/li>\n\n\n\n
    • Email<\/code> \u2192 UNIQUE<\/li>\n\n\n\n
    • StudentID<\/code> in Result<\/code> \u2192 FOREIGN KEY<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"
      The constraints you listed are Integrity Constraints in DBMS\/RDBMS. They help maintain the accuracy and consistency of data. 1. NOT NULL Constraint Ensures that a column cannot have a NULL (empty) value. Example: Here, the Name column must contain a value. 2. UNIQUE Constraint Ensures that all values in a column are unique. Example: No […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[30],"tags":[],"class_list":["post-514","post","type-post","status-publish","format-standard","hentry","category-oracle"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/mitalgoswami.in\/index.php?rest_route=\/wp\/v2\/posts\/514","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/mitalgoswami.in\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mitalgoswami.in\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mitalgoswami.in\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/mitalgoswami.in\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=514"}],"version-history":[{"count":1,"href":"https:\/\/mitalgoswami.in\/index.php?rest_route=\/wp\/v2\/posts\/514\/revisions"}],"predecessor-version":[{"id":515,"href":"https:\/\/mitalgoswami.in\/index.php?rest_route=\/wp\/v2\/posts\/514\/revisions\/515"}],"wp:attachment":[{"href":"https:\/\/mitalgoswami.in\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=514"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mitalgoswami.in\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=514"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mitalgoswami.in\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=514"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}