{"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 loading=\"lazy\" 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=IQoJb3JpZ2luX2VjEBIaCWV1LXdlc3QtMSJGMEQCIHC%2B3ahoBoMFStgZ4EUYoIbQwmqJ0BCRV72SMvnizAgCAiBYQziHH93Sy%2FkyGrTtPEVBNShNxcv2GJqWX4Bqq7paYCrCBQjb%2F%2F%2F%2F%2F%2F%2F%2F%2F%2F8BEAUaDDI3MzU3MDE5NTQzMyIMW5zNnWaC3MgGQnEiKpYFwE1whE8zqcJ6JGrKH29kyP6MG2A6Wu8m3F72GAZ3ygyz%2BtHvIH%2FPlBH2UsWiDgIgRSk2kNGUSAKx4zKCqIX%2Fhrz4wv4MG%2BVH7irgIqktTlVDpJjEBmcPH43jB6BwSVj9FZp0O5BjqDAkGmqHeQu66Jedng6mI2worNT0tPAs6yptJW8SrMFoPSf9kGNPv0KSEhPg6xABzRrOd3reGfta%2Fjl14ta0aEpId77wSStEQ8ElzF%2BQk%2B%2FzVe1G0KYScxu%2FJhV%2B5jk1As3hQDNFZeWkjSFlkoKKkuWy0%2F5rI2tsnag7XKKnliFgshbHhhAkP2MoQ7rYa45ourfPT%2BO%2BlrB0udHciVbsAftoTrazarzb%2B3xpsA8Hbg0jE9MEmNd3yi3I6IpjNID56WR%2BqS4vbD1YJITcpVg7LY2Bg4dU3MkcHc%2FBW3eia%2FymX4dlFVUXajg%2F8JtiWPJ9QGnERJRrZbZLb2TdF30IVbqWyfTiN9c6Rh46odNsRePgD0qRh8ycJJbOEwXgGm5OB29%2BOyQyEtduEd5B0k9av7AndO3ErHLvy7j9xlwKXCeoDJJk5Rt4UztI8pMp5ZAg1UoGvSSQKcBre8jwnS7Xn7Xo8p9ok3290CVXobZ96Yl8P00%2FK22B219WRrxse091SVa4EcvwGgNA7WdbfrgYEhdyHcq8lhB2aGVZ%2FcrYKsxxYQyopoSbqToZR2dYC3KEsfBICknFobva6aVFxeds0x54bwwLp25T71tnbd4K9%2Fe7CJj2Z9ojv%2F3WO0e%2FLM9IceEkoQlz0sG0olIXkyFLEQAVi%2BrQDQ%2BDiUT7Qa%2Bb58%2FOnBtXGQu7WLD%2FqRWfPeD%2BzD1zSLZyKgmyEAGTYnqLExn%2FQZ65Xr0V5jGNRepVEGcwgf%2FBzwY6sgFlIrZ6XQjsrkVgD26uXck92s4KuKYf8Jvy0bkS8iejP6yST5q9hWNhw52FbNSz9SLuRR5kuq1bmOugy6KylQa6bBVwIonsFZM0CqkWAC%2F1%2BRiRYqX20%2FUVyQNF%2FYqTtg8BE4uvHEFbKz6LmsBBH6v%2B%2FOtmXBx4Hlh00fEnWkZv5BGEwZVQ%2B8fV7gIzV7ec6KL5GIsvU0LFqVLGH2VYloM%2FsHTa8Ois9XNWPvJD0mFjgX7F&amp;X-Amz-Algorithm=AWS4-HMAC-SHA256&amp;X-Amz-Credential=ASIAT7MQN47UTPUJFTYH%2F20260428%2Feu-west-1%2Fs3%2Faws4_request&amp;X-Amz-Date=20260428T101636Z&amp;X-Amz-SignedHeaders=host&amp;X-Amz-Expires=900&amp;X-Amz-Signature=b624dc2ddd1e5d453b82a8931154e99ef9680607ae5d4ceffc885f59f8cd8582 300w\" sizes=\"auto, (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 loading=\"lazy\" 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=IQoJb3JpZ2luX2VjEBIaCWV1LXdlc3QtMSJGMEQCIHC%2B3ahoBoMFStgZ4EUYoIbQwmqJ0BCRV72SMvnizAgCAiBYQziHH93Sy%2FkyGrTtPEVBNShNxcv2GJqWX4Bqq7paYCrCBQjb%2F%2F%2F%2F%2F%2F%2F%2F%2F%2F8BEAUaDDI3MzU3MDE5NTQzMyIMW5zNnWaC3MgGQnEiKpYFwE1whE8zqcJ6JGrKH29kyP6MG2A6Wu8m3F72GAZ3ygyz%2BtHvIH%2FPlBH2UsWiDgIgRSk2kNGUSAKx4zKCqIX%2Fhrz4wv4MG%2BVH7irgIqktTlVDpJjEBmcPH43jB6BwSVj9FZp0O5BjqDAkGmqHeQu66Jedng6mI2worNT0tPAs6yptJW8SrMFoPSf9kGNPv0KSEhPg6xABzRrOd3reGfta%2Fjl14ta0aEpId77wSStEQ8ElzF%2BQk%2B%2FzVe1G0KYScxu%2FJhV%2B5jk1As3hQDNFZeWkjSFlkoKKkuWy0%2F5rI2tsnag7XKKnliFgshbHhhAkP2MoQ7rYa45ourfPT%2BO%2BlrB0udHciVbsAftoTrazarzb%2B3xpsA8Hbg0jE9MEmNd3yi3I6IpjNID56WR%2BqS4vbD1YJITcpVg7LY2Bg4dU3MkcHc%2FBW3eia%2FymX4dlFVUXajg%2F8JtiWPJ9QGnERJRrZbZLb2TdF30IVbqWyfTiN9c6Rh46odNsRePgD0qRh8ycJJbOEwXgGm5OB29%2BOyQyEtduEd5B0k9av7AndO3ErHLvy7j9xlwKXCeoDJJk5Rt4UztI8pMp5ZAg1UoGvSSQKcBre8jwnS7Xn7Xo8p9ok3290CVXobZ96Yl8P00%2FK22B219WRrxse091SVa4EcvwGgNA7WdbfrgYEhdyHcq8lhB2aGVZ%2FcrYKsxxYQyopoSbqToZR2dYC3KEsfBICknFobva6aVFxeds0x54bwwLp25T71tnbd4K9%2Fe7CJj2Z9ojv%2F3WO0e%2FLM9IceEkoQlz0sG0olIXkyFLEQAVi%2BrQDQ%2BDiUT7Qa%2Bb58%2FOnBtXGQu7WLD%2FqRWfPeD%2BzD1zSLZyKgmyEAGTYnqLExn%2FQZ65Xr0V5jGNRepVEGcwgf%2FBzwY6sgFlIrZ6XQjsrkVgD26uXck92s4KuKYf8Jvy0bkS8iejP6yST5q9hWNhw52FbNSz9SLuRR5kuq1bmOugy6KylQa6bBVwIonsFZM0CqkWAC%2F1%2BRiRYqX20%2FUVyQNF%2FYqTtg8BE4uvHEFbKz6LmsBBH6v%2B%2FOtmXBx4Hlh00fEnWkZv5BGEwZVQ%2B8fV7gIzV7ec6KL5GIsvU0LFqVLGH2VYloM%2FsHTa8Ois9XNWPvJD0mFjgX7F&amp;X-Amz-Algorithm=AWS4-HMAC-SHA256&amp;X-Amz-Credential=ASIAT7MQN47UTPUJFTYH%2F20260428%2Feu-west-1%2Fs3%2Faws4_request&amp;X-Amz-Date=20260428T101636Z&amp;X-Amz-SignedHeaders=host&amp;X-Amz-Expires=900&amp;X-Amz-Signature=acd6ae73b66649b6f76756fe52d02943710d609257cc9cfe7bd00a7c345f76ae 300w\" sizes=\"auto, (max-width: 334px) 100vw, 334px\" \/><\/li>\n<li>Widen the table so you can see the Foreign Key column<br \/>\n<img loading=\"lazy\" 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=IQoJb3JpZ2luX2VjEBIaCWV1LXdlc3QtMSJGMEQCIHC%2B3ahoBoMFStgZ4EUYoIbQwmqJ0BCRV72SMvnizAgCAiBYQziHH93Sy%2FkyGrTtPEVBNShNxcv2GJqWX4Bqq7paYCrCBQjb%2F%2F%2F%2F%2F%2F%2F%2F%2F%2F8BEAUaDDI3MzU3MDE5NTQzMyIMW5zNnWaC3MgGQnEiKpYFwE1whE8zqcJ6JGrKH29kyP6MG2A6Wu8m3F72GAZ3ygyz%2BtHvIH%2FPlBH2UsWiDgIgRSk2kNGUSAKx4zKCqIX%2Fhrz4wv4MG%2BVH7irgIqktTlVDpJjEBmcPH43jB6BwSVj9FZp0O5BjqDAkGmqHeQu66Jedng6mI2worNT0tPAs6yptJW8SrMFoPSf9kGNPv0KSEhPg6xABzRrOd3reGfta%2Fjl14ta0aEpId77wSStEQ8ElzF%2BQk%2B%2FzVe1G0KYScxu%2FJhV%2B5jk1As3hQDNFZeWkjSFlkoKKkuWy0%2F5rI2tsnag7XKKnliFgshbHhhAkP2MoQ7rYa45ourfPT%2BO%2BlrB0udHciVbsAftoTrazarzb%2B3xpsA8Hbg0jE9MEmNd3yi3I6IpjNID56WR%2BqS4vbD1YJITcpVg7LY2Bg4dU3MkcHc%2FBW3eia%2FymX4dlFVUXajg%2F8JtiWPJ9QGnERJRrZbZLb2TdF30IVbqWyfTiN9c6Rh46odNsRePgD0qRh8ycJJbOEwXgGm5OB29%2BOyQyEtduEd5B0k9av7AndO3ErHLvy7j9xlwKXCeoDJJk5Rt4UztI8pMp5ZAg1UoGvSSQKcBre8jwnS7Xn7Xo8p9ok3290CVXobZ96Yl8P00%2FK22B219WRrxse091SVa4EcvwGgNA7WdbfrgYEhdyHcq8lhB2aGVZ%2FcrYKsxxYQyopoSbqToZR2dYC3KEsfBICknFobva6aVFxeds0x54bwwLp25T71tnbd4K9%2Fe7CJj2Z9ojv%2F3WO0e%2FLM9IceEkoQlz0sG0olIXkyFLEQAVi%2BrQDQ%2BDiUT7Qa%2Bb58%2FOnBtXGQu7WLD%2FqRWfPeD%2BzD1zSLZyKgmyEAGTYnqLExn%2FQZ65Xr0V5jGNRepVEGcwgf%2FBzwY6sgFlIrZ6XQjsrkVgD26uXck92s4KuKYf8Jvy0bkS8iejP6yST5q9hWNhw52FbNSz9SLuRR5kuq1bmOugy6KylQa6bBVwIonsFZM0CqkWAC%2F1%2BRiRYqX20%2FUVyQNF%2FYqTtg8BE4uvHEFbKz6LmsBBH6v%2B%2FOtmXBx4Hlh00fEnWkZv5BGEwZVQ%2B8fV7gIzV7ec6KL5GIsvU0LFqVLGH2VYloM%2FsHTa8Ois9XNWPvJD0mFjgX7F&amp;X-Amz-Algorithm=AWS4-HMAC-SHA256&amp;X-Amz-Credential=ASIAT7MQN47UTPUJFTYH%2F20260428%2Feu-west-1%2Fs3%2Faws4_request&amp;X-Amz-Date=20260428T101636Z&amp;X-Amz-SignedHeaders=host&amp;X-Amz-Expires=900&amp;X-Amz-Signature=7da9b75f75dc009873d30e8919dfdb6b09ceee8d1522d26911dc4a1cf41a7c3c 300w\" sizes=\"auto, (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 loading=\"lazy\" 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=IQoJb3JpZ2luX2VjEBIaCWV1LXdlc3QtMSJGMEQCIHC%2B3ahoBoMFStgZ4EUYoIbQwmqJ0BCRV72SMvnizAgCAiBYQziHH93Sy%2FkyGrTtPEVBNShNxcv2GJqWX4Bqq7paYCrCBQjb%2F%2F%2F%2F%2F%2F%2F%2F%2F%2F8BEAUaDDI3MzU3MDE5NTQzMyIMW5zNnWaC3MgGQnEiKpYFwE1whE8zqcJ6JGrKH29kyP6MG2A6Wu8m3F72GAZ3ygyz%2BtHvIH%2FPlBH2UsWiDgIgRSk2kNGUSAKx4zKCqIX%2Fhrz4wv4MG%2BVH7irgIqktTlVDpJjEBmcPH43jB6BwSVj9FZp0O5BjqDAkGmqHeQu66Jedng6mI2worNT0tPAs6yptJW8SrMFoPSf9kGNPv0KSEhPg6xABzRrOd3reGfta%2Fjl14ta0aEpId77wSStEQ8ElzF%2BQk%2B%2FzVe1G0KYScxu%2FJhV%2B5jk1As3hQDNFZeWkjSFlkoKKkuWy0%2F5rI2tsnag7XKKnliFgshbHhhAkP2MoQ7rYa45ourfPT%2BO%2BlrB0udHciVbsAftoTrazarzb%2B3xpsA8Hbg0jE9MEmNd3yi3I6IpjNID56WR%2BqS4vbD1YJITcpVg7LY2Bg4dU3MkcHc%2FBW3eia%2FymX4dlFVUXajg%2F8JtiWPJ9QGnERJRrZbZLb2TdF30IVbqWyfTiN9c6Rh46odNsRePgD0qRh8ycJJbOEwXgGm5OB29%2BOyQyEtduEd5B0k9av7AndO3ErHLvy7j9xlwKXCeoDJJk5Rt4UztI8pMp5ZAg1UoGvSSQKcBre8jwnS7Xn7Xo8p9ok3290CVXobZ96Yl8P00%2FK22B219WRrxse091SVa4EcvwGgNA7WdbfrgYEhdyHcq8lhB2aGVZ%2FcrYKsxxYQyopoSbqToZR2dYC3KEsfBICknFobva6aVFxeds0x54bwwLp25T71tnbd4K9%2Fe7CJj2Z9ojv%2F3WO0e%2FLM9IceEkoQlz0sG0olIXkyFLEQAVi%2BrQDQ%2BDiUT7Qa%2Bb58%2FOnBtXGQu7WLD%2FqRWfPeD%2BzD1zSLZyKgmyEAGTYnqLExn%2FQZ65Xr0V5jGNRepVEGcwgf%2FBzwY6sgFlIrZ6XQjsrkVgD26uXck92s4KuKYf8Jvy0bkS8iejP6yST5q9hWNhw52FbNSz9SLuRR5kuq1bmOugy6KylQa6bBVwIonsFZM0CqkWAC%2F1%2BRiRYqX20%2FUVyQNF%2FYqTtg8BE4uvHEFbKz6LmsBBH6v%2B%2FOtmXBx4Hlh00fEnWkZv5BGEwZVQ%2B8fV7gIzV7ec6KL5GIsvU0LFqVLGH2VYloM%2FsHTa8Ois9XNWPvJD0mFjgX7F&amp;X-Amz-Algorithm=AWS4-HMAC-SHA256&amp;X-Amz-Credential=ASIAT7MQN47UTPUJFTYH%2F20260428%2Feu-west-1%2Fs3%2Faws4_request&amp;X-Amz-Date=20260428T101636Z&amp;X-Amz-SignedHeaders=host&amp;X-Amz-Expires=900&amp;X-Amz-Signature=93e95c5a69ae249b172f009449d95669b4316f2d46e00ea30012653ec022f399 300w\" sizes=\"auto, (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 loading=\"lazy\" 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=\"auto, (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}]}}