{"absolute_url": "/jbmckee/drop-the-constraint-if-it-exists/", "blog_post": false, "code": "-- Drop the constraint if it exists\nset @var=if((SELECT true FROM information_schema.TABLE_CONSTRAINTS WHERE\n   CONSTRAINT_SCHEMA = DATABASE() AND\n   TABLE_NAME        = 'bluebookfacts' AND\n   CONSTRAINT_NAME   = 'fk_bb_log_facts' AND\n   CONSTRAINT_TYPE   = 'FOREIGN KEY') = true,'ALTER TABLE bluebook DROP FOREIGN KEY fk_bb_log_facts', 'select 1');\nprepare stmt from @var;\nexecute stmt;\ndeallocate prepare stmt;", "created": "2017-02-08T15:16:53.248198", "description": "", "description_rendered": "", "embed_url": "https://snipt.net/embed/09601d166c92af3b299cd0cc0a3a8154/", "full_absolute_url": "/jbmckee/drop-the-constraint-if-it-exists/", "id": 11, "lexer": "text", "line_count": 9, "log_entries": [{"code": "-- Drop the constraint if it exists\nset @var=if((SELECT true FROM information_schema.TABLE_CONSTRAINTS WHERE\n   CONSTRAINT_SCHEMA = DATABASE() AND\n   TABLE_NAME        = 'bluebookfacts' AND\n   CONSTRAINT_NAME   = 'fk_bb_log_facts' AND\n   CONSTRAINT_TYPE   = 'FOREIGN KEY') = true,'ALTER TABLE bluebook DROP FOREIGN KEY fk_bb_log_facts', 'select 1');\nprepare stmt from @var;\nexecute stmt;\ndeallocate prepare stmt;", "created": "2017-02-08T15:16:54.130926", "diff": "--- \n+++ \n@@ -0,0 +1,9 @@\n+-- Drop the constraint if it exists\n+set @var=if((SELECT true FROM information_schema.TABLE_CONSTRAINTS WHERE\n+   CONSTRAINT_SCHEMA = DATABASE() AND\n+   TABLE_NAME        = 'bluebookfacts' AND\n+   CONSTRAINT_NAME   = 'fk_bb_log_facts' AND\n+   CONSTRAINT_TYPE   = 'FOREIGN KEY') = true,'ALTER TABLE bluebook DROP FOREIGN KEY fk_bb_log_facts', 'select 1');\n+prepare stmt from @var;\n+execute stmt;\n+deallocate prepare stmt;", "user": "jbmckee"}], "meta": "", "modified": "2026-04-27T03:46:05.923553", "publish_date": "2017-02-08T15:16:52.905541", "raw_url": "/raw/09601d166c92af3b299cd0cc0a3a8154/", "resource_uri": "/api/public/snipt/11/", "slug": "drop-the-constraint-if-it-exists", "stylized": "<table class=\"highlighttable\"><tr><td class=\"linenos\"><div class=\"linenodiv\"><pre><a href=\"#L-1\">1</a>\n<a href=\"#L-2\">2</a>\n<a href=\"#L-3\">3</a>\n<a href=\"#L-4\">4</a>\n<a href=\"#L-5\">5</a>\n<a href=\"#L-6\">6</a>\n<a href=\"#L-7\">7</a>\n<a href=\"#L-8\">8</a>\n<a href=\"#L-9\">9</a></pre></div></td><td class=\"code\"><div class=\"highlight\"><pre><span></span><span id=\"L-1\"><a name=\"L-1\"></a>-- Drop the constraint if it exists\n</span><span id=\"L-2\"><a name=\"L-2\"></a>set @var=if((SELECT true FROM information_schema.TABLE_CONSTRAINTS WHERE\n</span><span id=\"L-3\"><a name=\"L-3\"></a>   CONSTRAINT_SCHEMA = DATABASE() AND\n</span><span id=\"L-4\"><a name=\"L-4\"></a>   TABLE_NAME        = &#39;bluebookfacts&#39; AND\n</span><span id=\"L-5\"><a name=\"L-5\"></a>   CONSTRAINT_NAME   = &#39;fk_bb_log_facts&#39; AND\n</span><span id=\"L-6\"><a name=\"L-6\"></a>   CONSTRAINT_TYPE   = &#39;FOREIGN KEY&#39;) = true,&#39;ALTER TABLE bluebook DROP FOREIGN KEY fk_bb_log_facts&#39;, &#39;select 1&#39;);\n</span><span id=\"L-7\"><a name=\"L-7\"></a>prepare stmt from @var;\n</span><span id=\"L-8\"><a name=\"L-8\"></a>execute stmt;\n</span><span id=\"L-9\"><a name=\"L-9\"></a>deallocate prepare stmt;\n</span></pre></div>\n</td></tr></table>", "tags": [{"absolute_url": "/public/tag/mysql/", "id": 18, "name": "mysql", "resource_uri": "/api/public/tag/18/", "snipts": "/api/public/snipt/?tag=18"}], "title": "Drop the constraint if it exists", "user": {"absolute_url": "/jbmckee/", "email_md5": "f4da96308b6db1b0b19738a7c105d3da", "id": 1, "resource_uri": "/api/public/user/1/", "snipts": "/api/public/snipt/?user=1", "snipts_count": 72, "username": "jbmckee"}}