{"id":195,"date":"2021-03-22T14:54:38","date_gmt":"2021-03-22T14:54:38","guid":{"rendered":"https:\/\/blogs.glowscotland.org.uk\/sh\/ahscomputingsql\/?page_id=195"},"modified":"2021-03-25T15:36:53","modified_gmt":"2021-03-25T15:36:53","slug":"primary-key","status":"publish","type":"page","link":"https:\/\/blogs.glowscotland.org.uk\/sh\/ahscomputingsql\/creating-a-database\/primary-key\/","title":{"rendered":"Primary &amp; Foreign Keys"},"content":{"rendered":"<h1><span style=\"color: #339966\">Level &#8211; National 5+<\/span><\/h1>\n<h1>Primary Key<\/h1>\n<p>Every table should have a primary key &#8211; a unique identifier for each record.<\/p>\n<p>Primary keys are required (Not Null), and\u00a0must be unique<\/p>\n<ul>\n<li>Right-click on the Table name<\/li>\n<li>Select &#8220;Modify table&#8221;<\/li>\n<li>Tick the NN, PK and U options for the primary key<br \/>\n<img decoding=\"async\" class=\"alignnone size-full wp-image-301\" src=\"https:\/\/blogs.glowscotland.org.uk\/sh\/public\/ahscomputingsql\/uploads\/sites\/3269\/2021\/03\/24122947\/DB4SQL-primary-key.png\" alt=\"\" width=\"610\" height=\"82\" srcset=\"https:\/\/blogs.glowscotland.org.uk\/sh\/public\/ahscomputingsql\/uploads\/sites\/3269\/2021\/03\/24122947\/DB4SQL-primary-key.png 610w, https:\/\/glow-prod-sh.s3.eu-west-1.amazonaws.com\/sh\/public\/ahscomputingsql\/uploads\/sites\/3269\/2021\/03\/24122947\/DB4SQL-primary-key-300x40.png?X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&amp;X-Amz-Security-Token=IQoJb3JpZ2luX2VjEHYaCWV1LXdlc3QtMSJHMEUCIQDH1bRoFKovVTMprzUq%2BPTyL8evjE7zUsx8KPo5jZ%2BfqQIgAsD%2FQFnHLKCVswjVRUNhccjnHlkFybGWAJfxR7zO1zQquAUIPxAFGgwyNzM1NzAxOTU0MzMiDIf6QYAe7nQ9aiyCmiqVBapYyrMawizAY9u7JkICBGZLjryqIjapP6NAns9d%2F9EmYh9rYvUDrhLB%2Fdd5AAuHv%2FDfiyth20Jx6uac6hHBxyfv1Bk9q1%2F1vpVdgEmPdWelMBqy5lWbq%2Bq4SEh3CptVcjgDChuVu3B6cpFXt9J2xeZxPY64fTt%2FrF1L%2FZ%2BHoEzM7CQkfK%2Bf%2FLc8YSk7v4XrEyf5O2Rm8HwYVfYBNIdSWZ%2FA3cT8TDm%2Bo%2F4j3XGOZzTB0mh1A1EEBkWzbQYoh6RrQLL6OohPyv8d44jsnJ0E4lFG4HBJE0x1YYHlV9RP05kFfbG9c2toqLoIwuU%2Bqrc2MhTOEuvcHUclr5MWsv2nRY%2BZ0dcWa7vQoZ4bWA86A1IFkkmhT13kRE1%2BX%2Fs3avZyEV%2Bof5vVWnQn1%2BZdisGrPW%2Ft38UKV9MA1o%2FJTooLBEmucV58tW%2F6wZLlElUKgl%2Bb%2Bru6aEW9g35BBshXzqmuG2mVtUXosKq7zmDuPQjkzX5vrlqa%2Bh%2BZNQixH6LhE7Oh5sJh9hCFROy%2BZNw8adZeyEVI664ILlSPaXYkGSB0fbo1Rek9koXgpa6IzWYdbt2h0X04m9Tg80ZApSZeyCk5KIZK8s%2BlUEx0KyAT9Oxit2Xf4r%2BxTFkcohKnLmlgJ5lIDo9emNKPDXlugCwDWXREYjhsSeNPBwRH12S95b2RUyZuatePFFgyGuAyJxfIMe%2B%2BtsC4RHWQxEkF7HCBYKYHVbF1%2B%2FBNsX90c9VvfsIiCCtC0QATPdPbzaeFS4s0BKnAEWeKyy4zEHIT3Id%2BxnzP4vJ2FgZPWKrZlSZf0hD7jFBkPi3uHzyyyJ37qvzg1VezAKAcIHwsNqJIP5hid5QctZtent%2F5w8kX78I9kBr5QGkxpP3Q4nIwhP2Z0wY6sQGgpTqhnmH1P3lW57nNVRvnfMpzL7e8XAyYZhJdHXwh8yqOuOwCc3PaZkH9Az6PhBPagQSn08Seph65pzhtQfp%2Fmo1a%2BUzFbI9gK7VjdhV2iglzdawM6Zj3YJ70rD4uDn6DRujvjJ5Yb2CfgL2b6sJo7hFvLzFRS9V8vbOZJPO7a8Vm1xyPpL6b5g80j9o2DNqY%2ByOXWcDmRZ1cRsJxrdKMTrFqbXF9qKUBvX28b6nUhA8%3D&amp;X-Amz-Algorithm=AWS4-HMAC-SHA256&amp;X-Amz-Credential=ASIAT7MQN47U2DCWGLX3%2F20260726%2Feu-west-1%2Fs3%2Faws4_request&amp;X-Amz-Date=20260726T220245Z&amp;X-Amz-SignedHeaders=host&amp;X-Amz-Expires=900&amp;X-Amz-Signature=659593a333c6cb07e9bb6aad7b0d2e1cc8f29a83fe87aedfb3520814d7656e7d 300w\" sizes=\"(max-width: 610px) 100vw, 610px\" \/><\/li>\n<\/ul>\n<hr \/>\n<h1>Foreign Key<\/h1>\n<p>A foreign key connects each record in a table to a record in another table. The other table must be created before the tables can be linked.<br \/>\n<em>eg Each record in &#8220;appointments&#8221; table will link to a customer. The customers table must be created before the appointments table.<\/em><\/p>\n<ul>\n<li>Right-click on the Table that has the foreign key<\/li>\n<li>Select &#8220;Modify table&#8221;<br \/>\n<img decoding=\"async\" class=\"alignnone size-full wp-image-308\" src=\"https:\/\/blogs.glowscotland.org.uk\/sh\/public\/ahscomputingsql\/uploads\/sites\/3269\/2021\/03\/24125204\/DB4SQL-foreignkey-1.png\" alt=\"\" width=\"334\" height=\"160\" srcset=\"https:\/\/blogs.glowscotland.org.uk\/sh\/public\/ahscomputingsql\/uploads\/sites\/3269\/2021\/03\/24125204\/DB4SQL-foreignkey-1.png 334w, https:\/\/glow-prod-sh.s3.eu-west-1.amazonaws.com\/sh\/public\/ahscomputingsql\/uploads\/sites\/3269\/2021\/03\/24125204\/DB4SQL-foreignkey-1-300x144.png?X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&amp;X-Amz-Security-Token=IQoJb3JpZ2luX2VjEHYaCWV1LXdlc3QtMSJHMEUCIQDH1bRoFKovVTMprzUq%2BPTyL8evjE7zUsx8KPo5jZ%2BfqQIgAsD%2FQFnHLKCVswjVRUNhccjnHlkFybGWAJfxR7zO1zQquAUIPxAFGgwyNzM1NzAxOTU0MzMiDIf6QYAe7nQ9aiyCmiqVBapYyrMawizAY9u7JkICBGZLjryqIjapP6NAns9d%2F9EmYh9rYvUDrhLB%2Fdd5AAuHv%2FDfiyth20Jx6uac6hHBxyfv1Bk9q1%2F1vpVdgEmPdWelMBqy5lWbq%2Bq4SEh3CptVcjgDChuVu3B6cpFXt9J2xeZxPY64fTt%2FrF1L%2FZ%2BHoEzM7CQkfK%2Bf%2FLc8YSk7v4XrEyf5O2Rm8HwYVfYBNIdSWZ%2FA3cT8TDm%2Bo%2F4j3XGOZzTB0mh1A1EEBkWzbQYoh6RrQLL6OohPyv8d44jsnJ0E4lFG4HBJE0x1YYHlV9RP05kFfbG9c2toqLoIwuU%2Bqrc2MhTOEuvcHUclr5MWsv2nRY%2BZ0dcWa7vQoZ4bWA86A1IFkkmhT13kRE1%2BX%2Fs3avZyEV%2Bof5vVWnQn1%2BZdisGrPW%2Ft38UKV9MA1o%2FJTooLBEmucV58tW%2F6wZLlElUKgl%2Bb%2Bru6aEW9g35BBshXzqmuG2mVtUXosKq7zmDuPQjkzX5vrlqa%2Bh%2BZNQixH6LhE7Oh5sJh9hCFROy%2BZNw8adZeyEVI664ILlSPaXYkGSB0fbo1Rek9koXgpa6IzWYdbt2h0X04m9Tg80ZApSZeyCk5KIZK8s%2BlUEx0KyAT9Oxit2Xf4r%2BxTFkcohKnLmlgJ5lIDo9emNKPDXlugCwDWXREYjhsSeNPBwRH12S95b2RUyZuatePFFgyGuAyJxfIMe%2B%2BtsC4RHWQxEkF7HCBYKYHVbF1%2B%2FBNsX90c9VvfsIiCCtC0QATPdPbzaeFS4s0BKnAEWeKyy4zEHIT3Id%2BxnzP4vJ2FgZPWKrZlSZf0hD7jFBkPi3uHzyyyJ37qvzg1VezAKAcIHwsNqJIP5hid5QctZtent%2F5w8kX78I9kBr5QGkxpP3Q4nIwhP2Z0wY6sQGgpTqhnmH1P3lW57nNVRvnfMpzL7e8XAyYZhJdHXwh8yqOuOwCc3PaZkH9Az6PhBPagQSn08Seph65pzhtQfp%2Fmo1a%2BUzFbI9gK7VjdhV2iglzdawM6Zj3YJ70rD4uDn6DRujvjJ5Yb2CfgL2b6sJo7hFvLzFRS9V8vbOZJPO7a8Vm1xyPpL6b5g80j9o2DNqY%2ByOXWcDmRZ1cRsJxrdKMTrFqbXF9qKUBvX28b6nUhA8%3D&amp;X-Amz-Algorithm=AWS4-HMAC-SHA256&amp;X-Amz-Credential=ASIAT7MQN47U2DCWGLX3%2F20260726%2Feu-west-1%2Fs3%2Faws4_request&amp;X-Amz-Date=20260726T220245Z&amp;X-Amz-SignedHeaders=host&amp;X-Amz-Expires=900&amp;X-Amz-Signature=9fc74c928702ec86b9b903dfd6f183bce4ef721deea736b78a9073fde92aeede 300w\" sizes=\"(max-width: 334px) 100vw, 334px\" \/><\/li>\n<li>Widen the table so you can see the Foreign Key column<br \/>\n<img decoding=\"async\" class=\"alignnone size-full wp-image-307\" src=\"https:\/\/blogs.glowscotland.org.uk\/sh\/public\/ahscomputingsql\/uploads\/sites\/3269\/2021\/03\/24125203\/DB4SQL-foreignkey-2.png\" alt=\"\" width=\"497\" height=\"160\" srcset=\"https:\/\/blogs.glowscotland.org.uk\/sh\/public\/ahscomputingsql\/uploads\/sites\/3269\/2021\/03\/24125203\/DB4SQL-foreignkey-2.png 497w, https:\/\/glow-prod-sh.s3.eu-west-1.amazonaws.com\/sh\/public\/ahscomputingsql\/uploads\/sites\/3269\/2021\/03\/24125203\/DB4SQL-foreignkey-2-300x97.png?X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&amp;X-Amz-Security-Token=IQoJb3JpZ2luX2VjEHYaCWV1LXdlc3QtMSJHMEUCIQDH1bRoFKovVTMprzUq%2BPTyL8evjE7zUsx8KPo5jZ%2BfqQIgAsD%2FQFnHLKCVswjVRUNhccjnHlkFybGWAJfxR7zO1zQquAUIPxAFGgwyNzM1NzAxOTU0MzMiDIf6QYAe7nQ9aiyCmiqVBapYyrMawizAY9u7JkICBGZLjryqIjapP6NAns9d%2F9EmYh9rYvUDrhLB%2Fdd5AAuHv%2FDfiyth20Jx6uac6hHBxyfv1Bk9q1%2F1vpVdgEmPdWelMBqy5lWbq%2Bq4SEh3CptVcjgDChuVu3B6cpFXt9J2xeZxPY64fTt%2FrF1L%2FZ%2BHoEzM7CQkfK%2Bf%2FLc8YSk7v4XrEyf5O2Rm8HwYVfYBNIdSWZ%2FA3cT8TDm%2Bo%2F4j3XGOZzTB0mh1A1EEBkWzbQYoh6RrQLL6OohPyv8d44jsnJ0E4lFG4HBJE0x1YYHlV9RP05kFfbG9c2toqLoIwuU%2Bqrc2MhTOEuvcHUclr5MWsv2nRY%2BZ0dcWa7vQoZ4bWA86A1IFkkmhT13kRE1%2BX%2Fs3avZyEV%2Bof5vVWnQn1%2BZdisGrPW%2Ft38UKV9MA1o%2FJTooLBEmucV58tW%2F6wZLlElUKgl%2Bb%2Bru6aEW9g35BBshXzqmuG2mVtUXosKq7zmDuPQjkzX5vrlqa%2Bh%2BZNQixH6LhE7Oh5sJh9hCFROy%2BZNw8adZeyEVI664ILlSPaXYkGSB0fbo1Rek9koXgpa6IzWYdbt2h0X04m9Tg80ZApSZeyCk5KIZK8s%2BlUEx0KyAT9Oxit2Xf4r%2BxTFkcohKnLmlgJ5lIDo9emNKPDXlugCwDWXREYjhsSeNPBwRH12S95b2RUyZuatePFFgyGuAyJxfIMe%2B%2BtsC4RHWQxEkF7HCBYKYHVbF1%2B%2FBNsX90c9VvfsIiCCtC0QATPdPbzaeFS4s0BKnAEWeKyy4zEHIT3Id%2BxnzP4vJ2FgZPWKrZlSZf0hD7jFBkPi3uHzyyyJ37qvzg1VezAKAcIHwsNqJIP5hid5QctZtent%2F5w8kX78I9kBr5QGkxpP3Q4nIwhP2Z0wY6sQGgpTqhnmH1P3lW57nNVRvnfMpzL7e8XAyYZhJdHXwh8yqOuOwCc3PaZkH9Az6PhBPagQSn08Seph65pzhtQfp%2Fmo1a%2BUzFbI9gK7VjdhV2iglzdawM6Zj3YJ70rD4uDn6DRujvjJ5Yb2CfgL2b6sJo7hFvLzFRS9V8vbOZJPO7a8Vm1xyPpL6b5g80j9o2DNqY%2ByOXWcDmRZ1cRsJxrdKMTrFqbXF9qKUBvX28b6nUhA8%3D&amp;X-Amz-Algorithm=AWS4-HMAC-SHA256&amp;X-Amz-Credential=ASIAT7MQN47U2DCWGLX3%2F20260726%2Feu-west-1%2Fs3%2Faws4_request&amp;X-Amz-Date=20260726T220245Z&amp;X-Amz-SignedHeaders=host&amp;X-Amz-Expires=900&amp;X-Amz-Signature=10121419ed718e5f693abf8c82f5dc051eb23a0d2916db82b8e13772b77bd542 300w\" sizes=\"(max-width: 497px) 100vw, 497px\" \/><\/li>\n<\/ul>\n<ul>\n<li>Double-click where the foreign key row and the Foreign Key column cross:<br \/>\n<img decoding=\"async\" class=\"alignnone size-full wp-image-309\" src=\"https:\/\/blogs.glowscotland.org.uk\/sh\/public\/ahscomputingsql\/uploads\/sites\/3269\/2021\/03\/24125636\/DB4SQL-foreignkey-3.png\" alt=\"\" width=\"606\" height=\"83\" srcset=\"https:\/\/blogs.glowscotland.org.uk\/sh\/public\/ahscomputingsql\/uploads\/sites\/3269\/2021\/03\/24125636\/DB4SQL-foreignkey-3.png 606w, https:\/\/glow-prod-sh.s3.eu-west-1.amazonaws.com\/sh\/public\/ahscomputingsql\/uploads\/sites\/3269\/2021\/03\/24125636\/DB4SQL-foreignkey-3-300x41.png?X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&amp;X-Amz-Security-Token=IQoJb3JpZ2luX2VjEHYaCWV1LXdlc3QtMSJHMEUCIQDH1bRoFKovVTMprzUq%2BPTyL8evjE7zUsx8KPo5jZ%2BfqQIgAsD%2FQFnHLKCVswjVRUNhccjnHlkFybGWAJfxR7zO1zQquAUIPxAFGgwyNzM1NzAxOTU0MzMiDIf6QYAe7nQ9aiyCmiqVBapYyrMawizAY9u7JkICBGZLjryqIjapP6NAns9d%2F9EmYh9rYvUDrhLB%2Fdd5AAuHv%2FDfiyth20Jx6uac6hHBxyfv1Bk9q1%2F1vpVdgEmPdWelMBqy5lWbq%2Bq4SEh3CptVcjgDChuVu3B6cpFXt9J2xeZxPY64fTt%2FrF1L%2FZ%2BHoEzM7CQkfK%2Bf%2FLc8YSk7v4XrEyf5O2Rm8HwYVfYBNIdSWZ%2FA3cT8TDm%2Bo%2F4j3XGOZzTB0mh1A1EEBkWzbQYoh6RrQLL6OohPyv8d44jsnJ0E4lFG4HBJE0x1YYHlV9RP05kFfbG9c2toqLoIwuU%2Bqrc2MhTOEuvcHUclr5MWsv2nRY%2BZ0dcWa7vQoZ4bWA86A1IFkkmhT13kRE1%2BX%2Fs3avZyEV%2Bof5vVWnQn1%2BZdisGrPW%2Ft38UKV9MA1o%2FJTooLBEmucV58tW%2F6wZLlElUKgl%2Bb%2Bru6aEW9g35BBshXzqmuG2mVtUXosKq7zmDuPQjkzX5vrlqa%2Bh%2BZNQixH6LhE7Oh5sJh9hCFROy%2BZNw8adZeyEVI664ILlSPaXYkGSB0fbo1Rek9koXgpa6IzWYdbt2h0X04m9Tg80ZApSZeyCk5KIZK8s%2BlUEx0KyAT9Oxit2Xf4r%2BxTFkcohKnLmlgJ5lIDo9emNKPDXlugCwDWXREYjhsSeNPBwRH12S95b2RUyZuatePFFgyGuAyJxfIMe%2B%2BtsC4RHWQxEkF7HCBYKYHVbF1%2B%2FBNsX90c9VvfsIiCCtC0QATPdPbzaeFS4s0BKnAEWeKyy4zEHIT3Id%2BxnzP4vJ2FgZPWKrZlSZf0hD7jFBkPi3uHzyyyJ37qvzg1VezAKAcIHwsNqJIP5hid5QctZtent%2F5w8kX78I9kBr5QGkxpP3Q4nIwhP2Z0wY6sQGgpTqhnmH1P3lW57nNVRvnfMpzL7e8XAyYZhJdHXwh8yqOuOwCc3PaZkH9Az6PhBPagQSn08Seph65pzhtQfp%2Fmo1a%2BUzFbI9gK7VjdhV2iglzdawM6Zj3YJ70rD4uDn6DRujvjJ5Yb2CfgL2b6sJo7hFvLzFRS9V8vbOZJPO7a8Vm1xyPpL6b5g80j9o2DNqY%2ByOXWcDmRZ1cRsJxrdKMTrFqbXF9qKUBvX28b6nUhA8%3D&amp;X-Amz-Algorithm=AWS4-HMAC-SHA256&amp;X-Amz-Credential=ASIAT7MQN47U2DCWGLX3%2F20260726%2Feu-west-1%2Fs3%2Faws4_request&amp;X-Amz-Date=20260726T220245Z&amp;X-Amz-SignedHeaders=host&amp;X-Amz-Expires=900&amp;X-Amz-Signature=9a4b9bb6602adf671101e0d6fdb35f4a89fceb82919cc6fa8f61857cb9f52628 300w\" sizes=\"(max-width: 606px) 100vw, 606px\" \/><\/li>\n<li>Use the drop-down menus to select the other table, and its primary key:<br \/>\n<img decoding=\"async\" class=\"alignnone size-full wp-image-310\" src=\"https:\/\/blogs.glowscotland.org.uk\/sh\/public\/ahscomputingsql\/uploads\/sites\/3269\/2021\/03\/24125850\/DB4SQL-foreignkey-4.png\" alt=\"\" width=\"607\" height=\"87\" srcset=\"https:\/\/blogs.glowscotland.org.uk\/sh\/public\/ahscomputingsql\/uploads\/sites\/3269\/2021\/03\/24125850\/DB4SQL-foreignkey-4.png 607w, 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300w\" sizes=\"(max-width: 607px) 100vw, 607px\" \/><\/li>\n<li>Click inside the grey &#8220;Foreign key clauses&#8230;&#8221; box, and press the Enter key<\/li>\n<li>Check the code in the bottom panel, and press the OK button<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>Level &#8211; National 5+ Primary Key Every table should have a primary key &#8211; a unique identifier for each record. Primary keys are required (Not Null), and\u00a0must be unique Right-click on the Table name Select &#8220;Modify table&#8221; Tick the NN, PK and U options for the primary key Foreign Key A foreign key connects each record in a table to a record in another table. The other table must be<\/p>\n<p><a class=\"more-link\" href=\"https:\/\/blogs.glowscotland.org.uk\/sh\/ahscomputingsql\/creating-a-database\/primary-key\/\">Read More<\/a><\/p>\n","protected":false},"author":7,"featured_media":0,"parent":262,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-195","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/blogs.glowscotland.org.uk\/sh\/ahscomputingsql\/wp-json\/wp\/v2\/pages\/195","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blogs.glowscotland.org.uk\/sh\/ahscomputingsql\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/blogs.glowscotland.org.uk\/sh\/ahscomputingsql\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.glowscotland.org.uk\/sh\/ahscomputingsql\/wp-json\/wp\/v2\/users\/7"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.glowscotland.org.uk\/sh\/ahscomputingsql\/wp-json\/wp\/v2\/comments?post=195"}],"version-history":[{"count":10,"href":"https:\/\/blogs.glowscotland.org.uk\/sh\/ahscomputingsql\/wp-json\/wp\/v2\/pages\/195\/revisions"}],"predecessor-version":[{"id":407,"href":"https:\/\/blogs.glowscotland.org.uk\/sh\/ahscomputingsql\/wp-json\/wp\/v2\/pages\/195\/revisions\/407"}],"up":[{"embeddable":true,"href":"https:\/\/blogs.glowscotland.org.uk\/sh\/ahscomputingsql\/wp-json\/wp\/v2\/pages\/262"}],"wp:attachment":[{"href":"https:\/\/blogs.glowscotland.org.uk\/sh\/ahscomputingsql\/wp-json\/wp\/v2\/media?parent=195"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}