{"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=IQoJb3JpZ2luX2VjELD%2F%2F%2F%2F%2F%2F%2F%2F%2F%2FwEaCWV1LXdlc3QtMSJIMEYCIQDnqdD%2Fq%2Be6%2Bb%2FOV6pVLjTeM1XUUtcIw4NYtnpED9oatQIhAPIJsw0YC9sTxTC9xOyzknREJndrxjEM%2FJNSlHqwSAYWKrkFCHkQBRoMMjczNTcwMTk1NDMzIgwUtJTz1AQcO8gf%2BbUqlgWA5lhQGnlnj7oOfDLQaCbhKMFBzemKVNO2QYep87vpKNAAPb9aAc%2FyzwGK7EoqB7Q%2BZjJFh8wpdO%2B3IeXyjPUTV63SgGopTb%2Bcr0CygV%2BTobaZCb1hmrqG%2B1so9cEZ0t%2FQo3ZMK7MzpfdRgqmGchujmYoflKrGYXQN1OaU0dXtuXqJtyapdwFmOwdA1EYm81BLiIG0iBbxywQzl32KYBgi0kD0KBfBVhkZ9hRiIMEh4dTpnOm3cpwnQ9StNCaxy9nuOYfdNkKWmU%2Fz6JT%2Fc25Kaj0BXck2cY1Qwr4i2vHe7uUcr0t9j%2F36LcWkVCwcgC5nz5enMiuBzeSjEgpkUGxvZH4yNyYgFjRHIPjhncn6pJizJAe%2Buk58n2PaVmaiW7tql9492G0zK3Ht58YcaueAdSWBxSAoimGRxpc103W6PFVsJ7oLmG4sAyWhhbqqQIqQqCOBoSVduFh9Z0HZZFQBufCg5%2F%2Ff4J2yi2OGAvxhf%2FDM8fK6DSvXdFu7bR2Zdm5DwEm%2BGGmICHaI6FXiBDkaxTIuRqubcXaH8IRUsdjJ2%2BOV2EDEdZg17qy7bAv1qqz3sF7fGG8W6%2FX%2FsRxDi%2Fw4adIhNtXMMIAy42a9BkNp%2Bhj%2Bsab9xKGf4aocfw4RUC00Rzlc6EAA3yUPTC1FWQai81Xf8lKCmLE1chxjN1R%2BHO0vO3gAhaD5DeSnt1new4gd%2F59ocn6RRqUUA0KXqRnGsZB%2BmPsR0T71gShVVR0cBGt4zp1rdmJ1SjoHdORJrUpG4ahufU8IEG%2BE6FPn7NQJaZxWqmegPQwK7n8AbMv3qXHKA50SkwPVZ9vpV6gr5C8if64mRMdtu2nXsk1GdyzxxI2aVkwRSS5zfizWtvLNF8r1iRKwojDi3OjWBjqwATR1PZnuGPCYyxuwxq00GOQTzeGY6F5DNXSM0iS6P17S%2FrDGUCLBQhL0qdfoL0LgAvSEfTz4pcalYgihB27dpnSqU%2FFjwQgaQf8cAfm%2FAU%2Bv1V44BRNlHrOD%2Bmem6KjB4a1C9nuEr2SLx6BzYEpJ6A%2BzqYlWF1iN7jG7JHx%2FrH1lFimtt4zFSPG2mpecK4q%2Fnxb2w5PSLNmgEXSoch6qMpGkvJLHxoa0vsmicAtZyn2J&amp;X-Amz-Algorithm=AWS4-HMAC-SHA256&amp;X-Amz-Credential=ASIAT7MQN47UXPFB5WQP%2F20261022%2Feu-west-1%2Fs3%2Faws4_request&amp;X-Amz-Date=20261022T160420Z&amp;X-Amz-SignedHeaders=host&amp;X-Amz-Expires=900&amp;X-Amz-Signature=c63a52c5ed8a10e563da3f4c64ad634b50d7e28241ce327b4fd33f19b40a90be 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=IQoJb3JpZ2luX2VjELD%2F%2F%2F%2F%2F%2F%2F%2F%2F%2FwEaCWV1LXdlc3QtMSJIMEYCIQDnqdD%2Fq%2Be6%2Bb%2FOV6pVLjTeM1XUUtcIw4NYtnpED9oatQIhAPIJsw0YC9sTxTC9xOyzknREJndrxjEM%2FJNSlHqwSAYWKrkFCHkQBRoMMjczNTcwMTk1NDMzIgwUtJTz1AQcO8gf%2BbUqlgWA5lhQGnlnj7oOfDLQaCbhKMFBzemKVNO2QYep87vpKNAAPb9aAc%2FyzwGK7EoqB7Q%2BZjJFh8wpdO%2B3IeXyjPUTV63SgGopTb%2Bcr0CygV%2BTobaZCb1hmrqG%2B1so9cEZ0t%2FQo3ZMK7MzpfdRgqmGchujmYoflKrGYXQN1OaU0dXtuXqJtyapdwFmOwdA1EYm81BLiIG0iBbxywQzl32KYBgi0kD0KBfBVhkZ9hRiIMEh4dTpnOm3cpwnQ9StNCaxy9nuOYfdNkKWmU%2Fz6JT%2Fc25Kaj0BXck2cY1Qwr4i2vHe7uUcr0t9j%2F36LcWkVCwcgC5nz5enMiuBzeSjEgpkUGxvZH4yNyYgFjRHIPjhncn6pJizJAe%2Buk58n2PaVmaiW7tql9492G0zK3Ht58YcaueAdSWBxSAoimGRxpc103W6PFVsJ7oLmG4sAyWhhbqqQIqQqCOBoSVduFh9Z0HZZFQBufCg5%2F%2Ff4J2yi2OGAvxhf%2FDM8fK6DSvXdFu7bR2Zdm5DwEm%2BGGmICHaI6FXiBDkaxTIuRqubcXaH8IRUsdjJ2%2BOV2EDEdZg17qy7bAv1qqz3sF7fGG8W6%2FX%2FsRxDi%2Fw4adIhNtXMMIAy42a9BkNp%2Bhj%2Bsab9xKGf4aocfw4RUC00Rzlc6EAA3yUPTC1FWQai81Xf8lKCmLE1chxjN1R%2BHO0vO3gAhaD5DeSnt1new4gd%2F59ocn6RRqUUA0KXqRnGsZB%2BmPsR0T71gShVVR0cBGt4zp1rdmJ1SjoHdORJrUpG4ahufU8IEG%2BE6FPn7NQJaZxWqmegPQwK7n8AbMv3qXHKA50SkwPVZ9vpV6gr5C8if64mRMdtu2nXsk1GdyzxxI2aVkwRSS5zfizWtvLNF8r1iRKwojDi3OjWBjqwATR1PZnuGPCYyxuwxq00GOQTzeGY6F5DNXSM0iS6P17S%2FrDGUCLBQhL0qdfoL0LgAvSEfTz4pcalYgihB27dpnSqU%2FFjwQgaQf8cAfm%2FAU%2Bv1V44BRNlHrOD%2Bmem6KjB4a1C9nuEr2SLx6BzYEpJ6A%2BzqYlWF1iN7jG7JHx%2FrH1lFimtt4zFSPG2mpecK4q%2Fnxb2w5PSLNmgEXSoch6qMpGkvJLHxoa0vsmicAtZyn2J&amp;X-Amz-Algorithm=AWS4-HMAC-SHA256&amp;X-Amz-Credential=ASIAT7MQN47UXPFB5WQP%2F20261022%2Feu-west-1%2Fs3%2Faws4_request&amp;X-Amz-Date=20261022T160420Z&amp;X-Amz-SignedHeaders=host&amp;X-Amz-Expires=900&amp;X-Amz-Signature=320406434df2ce087007f97623445fa07a3137b17f05713e8550b3d9f34b5e74 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=IQoJb3JpZ2luX2VjELD%2F%2F%2F%2F%2F%2F%2F%2F%2F%2FwEaCWV1LXdlc3QtMSJIMEYCIQDnqdD%2Fq%2Be6%2Bb%2FOV6pVLjTeM1XUUtcIw4NYtnpED9oatQIhAPIJsw0YC9sTxTC9xOyzknREJndrxjEM%2FJNSlHqwSAYWKrkFCHkQBRoMMjczNTcwMTk1NDMzIgwUtJTz1AQcO8gf%2BbUqlgWA5lhQGnlnj7oOfDLQaCbhKMFBzemKVNO2QYep87vpKNAAPb9aAc%2FyzwGK7EoqB7Q%2BZjJFh8wpdO%2B3IeXyjPUTV63SgGopTb%2Bcr0CygV%2BTobaZCb1hmrqG%2B1so9cEZ0t%2FQo3ZMK7MzpfdRgqmGchujmYoflKrGYXQN1OaU0dXtuXqJtyapdwFmOwdA1EYm81BLiIG0iBbxywQzl32KYBgi0kD0KBfBVhkZ9hRiIMEh4dTpnOm3cpwnQ9StNCaxy9nuOYfdNkKWmU%2Fz6JT%2Fc25Kaj0BXck2cY1Qwr4i2vHe7uUcr0t9j%2F36LcWkVCwcgC5nz5enMiuBzeSjEgpkUGxvZH4yNyYgFjRHIPjhncn6pJizJAe%2Buk58n2PaVmaiW7tql9492G0zK3Ht58YcaueAdSWBxSAoimGRxpc103W6PFVsJ7oLmG4sAyWhhbqqQIqQqCOBoSVduFh9Z0HZZFQBufCg5%2F%2Ff4J2yi2OGAvxhf%2FDM8fK6DSvXdFu7bR2Zdm5DwEm%2BGGmICHaI6FXiBDkaxTIuRqubcXaH8IRUsdjJ2%2BOV2EDEdZg17qy7bAv1qqz3sF7fGG8W6%2FX%2FsRxDi%2Fw4adIhNtXMMIAy42a9BkNp%2Bhj%2Bsab9xKGf4aocfw4RUC00Rzlc6EAA3yUPTC1FWQai81Xf8lKCmLE1chxjN1R%2BHO0vO3gAhaD5DeSnt1new4gd%2F59ocn6RRqUUA0KXqRnGsZB%2BmPsR0T71gShVVR0cBGt4zp1rdmJ1SjoHdORJrUpG4ahufU8IEG%2BE6FPn7NQJaZxWqmegPQwK7n8AbMv3qXHKA50SkwPVZ9vpV6gr5C8if64mRMdtu2nXsk1GdyzxxI2aVkwRSS5zfizWtvLNF8r1iRKwojDi3OjWBjqwATR1PZnuGPCYyxuwxq00GOQTzeGY6F5DNXSM0iS6P17S%2FrDGUCLBQhL0qdfoL0LgAvSEfTz4pcalYgihB27dpnSqU%2FFjwQgaQf8cAfm%2FAU%2Bv1V44BRNlHrOD%2Bmem6KjB4a1C9nuEr2SLx6BzYEpJ6A%2BzqYlWF1iN7jG7JHx%2FrH1lFimtt4zFSPG2mpecK4q%2Fnxb2w5PSLNmgEXSoch6qMpGkvJLHxoa0vsmicAtZyn2J&amp;X-Amz-Algorithm=AWS4-HMAC-SHA256&amp;X-Amz-Credential=ASIAT7MQN47UXPFB5WQP%2F20261022%2Feu-west-1%2Fs3%2Faws4_request&amp;X-Amz-Date=20261022T160420Z&amp;X-Amz-SignedHeaders=host&amp;X-Amz-Expires=900&amp;X-Amz-Signature=181e63ebb568767952e791efac710d48ee156120e8108b7082ec362cb993f7aa 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=IQoJb3JpZ2luX2VjELD%2F%2F%2F%2F%2F%2F%2F%2F%2F%2FwEaCWV1LXdlc3QtMSJIMEYCIQDnqdD%2Fq%2Be6%2Bb%2FOV6pVLjTeM1XUUtcIw4NYtnpED9oatQIhAPIJsw0YC9sTxTC9xOyzknREJndrxjEM%2FJNSlHqwSAYWKrkFCHkQBRoMMjczNTcwMTk1NDMzIgwUtJTz1AQcO8gf%2BbUqlgWA5lhQGnlnj7oOfDLQaCbhKMFBzemKVNO2QYep87vpKNAAPb9aAc%2FyzwGK7EoqB7Q%2BZjJFh8wpdO%2B3IeXyjPUTV63SgGopTb%2Bcr0CygV%2BTobaZCb1hmrqG%2B1so9cEZ0t%2FQo3ZMK7MzpfdRgqmGchujmYoflKrGYXQN1OaU0dXtuXqJtyapdwFmOwdA1EYm81BLiIG0iBbxywQzl32KYBgi0kD0KBfBVhkZ9hRiIMEh4dTpnOm3cpwnQ9StNCaxy9nuOYfdNkKWmU%2Fz6JT%2Fc25Kaj0BXck2cY1Qwr4i2vHe7uUcr0t9j%2F36LcWkVCwcgC5nz5enMiuBzeSjEgpkUGxvZH4yNyYgFjRHIPjhncn6pJizJAe%2Buk58n2PaVmaiW7tql9492G0zK3Ht58YcaueAdSWBxSAoimGRxpc103W6PFVsJ7oLmG4sAyWhhbqqQIqQqCOBoSVduFh9Z0HZZFQBufCg5%2F%2Ff4J2yi2OGAvxhf%2FDM8fK6DSvXdFu7bR2Zdm5DwEm%2BGGmICHaI6FXiBDkaxTIuRqubcXaH8IRUsdjJ2%2BOV2EDEdZg17qy7bAv1qqz3sF7fGG8W6%2FX%2FsRxDi%2Fw4adIhNtXMMIAy42a9BkNp%2Bhj%2Bsab9xKGf4aocfw4RUC00Rzlc6EAA3yUPTC1FWQai81Xf8lKCmLE1chxjN1R%2BHO0vO3gAhaD5DeSnt1new4gd%2F59ocn6RRqUUA0KXqRnGsZB%2BmPsR0T71gShVVR0cBGt4zp1rdmJ1SjoHdORJrUpG4ahufU8IEG%2BE6FPn7NQJaZxWqmegPQwK7n8AbMv3qXHKA50SkwPVZ9vpV6gr5C8if64mRMdtu2nXsk1GdyzxxI2aVkwRSS5zfizWtvLNF8r1iRKwojDi3OjWBjqwATR1PZnuGPCYyxuwxq00GOQTzeGY6F5DNXSM0iS6P17S%2FrDGUCLBQhL0qdfoL0LgAvSEfTz4pcalYgihB27dpnSqU%2FFjwQgaQf8cAfm%2FAU%2Bv1V44BRNlHrOD%2Bmem6KjB4a1C9nuEr2SLx6BzYEpJ6A%2BzqYlWF1iN7jG7JHx%2FrH1lFimtt4zFSPG2mpecK4q%2Fnxb2w5PSLNmgEXSoch6qMpGkvJLHxoa0vsmicAtZyn2J&amp;X-Amz-Algorithm=AWS4-HMAC-SHA256&amp;X-Amz-Credential=ASIAT7MQN47UXPFB5WQP%2F20261022%2Feu-west-1%2Fs3%2Faws4_request&amp;X-Amz-Date=20261022T160420Z&amp;X-Amz-SignedHeaders=host&amp;X-Amz-Expires=900&amp;X-Amz-Signature=5f5c87d96cc7e1c2910cff498c78f680e55eab04718d1da01ed6030ceba97835 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}]}}