{"id":10642,"date":"2017-11-15T15:18:13","date_gmt":"2017-11-15T14:18:13","guid":{"rendered":"https:\/\/www.dbi-services.com\/blog\/can-i-do-it-with-postgresql-18-instead-of-triggers-on-views\/"},"modified":"2017-11-15T15:18:13","modified_gmt":"2017-11-15T14:18:13","slug":"can-i-do-it-with-postgresql-18-instead-of-triggers-on-views","status":"publish","type":"post","link":"https:\/\/www.dbi-services.com\/blog\/can-i-do-it-with-postgresql-18-instead-of-triggers-on-views\/","title":{"rendered":"Can I do it with PostgreSQL? \u2013 18 \u2013 Instead of triggers on views"},"content":{"rendered":"<p>It has been quite a while since the last post in this series but today comes the next one. Being at a customer this morning this question popped up: Can we have instead of triggers on a view in PostgreSQL as well? I couln&#8217;d immediately answer (although I was quite sure you can) so here is the test. I took an <a href=\"https:\/\/www.mkyong.com\/oracle\/oracle-plsql-instead-of-trigger-example\/\" target=\"_blank\" rel=\"noopener\">example for Oracle from here<\/a> and re-wrote it in PostgreSQL syntax.<\/p>\n<p><!--more--><\/p>\n<p>I took the same tables and adjusted the data types:<\/p>\n<pre class=\"brush: sql; gutter: true; first-line: 1\">\nCREATE TABLE CUSTOMER_DETAILS ( CUSTOMER_ID INT PRIMARY KEY\n                              , CUSTOMER_NAME VARCHAR(20)\n                              , COUNTRY VARCHAR(20)\n                              );\nCREATE TABLE PROJECTS_DETAILS ( PROJECT_ID INT PRIMARY KEY\n                              , PROJECT_NAME VARCHAR(30)\n                              , PROJECT_START_DATE DATE\n                              , CUSTOMER_ID INT REFERENCES CUSTOMER_DETAILS(CUSTOMER_ID)\n                              );\n<\/pre>\n<p>The same view definition:<\/p>\n<pre class=\"brush: sql; gutter: true; first-line: 1\">\nCREATE OR REPLACE VIEW customer_projects_view AS\n   SELECT cust.customer_id, cust.customer_name, cust.country,\n          projectdtls.project_id, projectdtls.project_name, \n          projectdtls.project_start_Date\n   FROM customer_details cust, projects_details projectdtls\n   WHERE cust.customer_id = projectdtls.customer_id;\n<\/pre>\n<p>Try to insert:<\/p>\n<pre class=\"brush: sql; gutter: true; first-line: 1\">\npostgres=# INSERT INTO customer_projects_view VALUES (1,'XYZ Enterprise','Japan',101,'Library management',now());\nERROR:  cannot insert into view \"customer_projects_view\"\nDETAIL:  Views that do not select from a single table or view are not automatically updatable.\nHINT:  To enable inserting into the view, provide an INSTEAD OF INSERT trigger or an unconditional ON INSERT DO INSTEAD rule.\nTime: 2.135 ms\n<\/pre>\n<p>&#8230; and the answer is already in the error message. So obviously we should be able to do that. In PostgreSQL you need a trigger function:<\/p>\n<pre class=\"brush: sql; gutter: true; first-line: 1\">\nCREATE OR REPLACE FUNCTION cust_proj_view_insert_proc() RETURNS trigger AS $$\nBEGIN\n        \n   INSERT INTO customer_details (customer_id,customer_name,country)\n          VALUES (NEW.customer_id, NEW.customer_name, NEW.country);\n\n   INSERT INTO projects_details (project_id, project_name, project_start_Date, customer_id)\n   VALUES (\n     NEW.project_id,\n     NEW.project_name,\n     NEW.project_start_Date,\n     NEW.customer_id);\n\n   RETURN NEW;\n     EXCEPTION WHEN unique_violation THEN\n       RAISE EXCEPTION 'Duplicate customer or project id';\nEND;\n$$ LANGUAGE plpgsql;\n<\/pre>\n<p>Then we need a trigger calling this function:<\/p>\n<pre class=\"brush: sql; gutter: true; first-line: 1\">\ncreate trigger cust_proj_view_insert_trg \n    instead of insert on customer_projects_view for each row EXECUTE procedure cust_proj_view_insert_proc();\n<\/pre>\n<p>Try the insert again:<\/p>\n<pre class=\"brush: sql; gutter: true; first-line: 1\">\nINSERT INTO customer_projects_view VALUES (1,'XYZ Enterprise','Japan',101,'Library management',now());\nINSERT INTO customer_projects_view VALUES (2,'ABC Infotech','India',202,'HR management',now());\n<\/pre>\n<p>&#8230; and here we are:<\/p>\n<pre class=\"brush: sql; gutter: true; first-line: 1\">\npostgres=# select * FROM customer_details;\n customer_id | customer_name  | country \n-------------+----------------+---------\n           1 | XYZ Enterprise | Japan\n           2 | ABC Infotech   | India\n<\/pre>\n<p>Definitely, you can \ud83d\ude42<\/p>\n","protected":false},"excerpt":{"rendered":"<p>It has been quite a while since the last post in this series but today comes the next one. Being at a customer this morning this question popped up: Can we have instead of triggers on a view in PostgreSQL as well? I couln&#8217;d immediately answer (although I was quite sure you can) so here [&hellip;]<\/p>\n","protected":false},"author":28,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[229],"tags":[77],"type_dbi":[],"class_list":["post-10642","post","type-post","status-publish","format-standard","hentry","category-database-administration-monitoring","tag-postgresql"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v28.8 (Yoast SEO v28.8) - https:\/\/yoast.com\/product\/yoast-seo-premium-wordpress\/ -->\n<title>Can I do it with PostgreSQL? \u2013 18 \u2013 Instead of triggers on views - dbi Blog<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.dbi-services.com\/blog\/can-i-do-it-with-postgresql-18-instead-of-triggers-on-views\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Can I do it with PostgreSQL? \u2013 18 \u2013 Instead of triggers on views\" \/>\n<meta property=\"og:description\" content=\"It has been quite a while since the last post in this series but today comes the next one. 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