{"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":29,"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 v27.2 (Yoast SEO v27.5) - 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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He has more than 15 years of experience in management, engineering and optimization of databases and infrastructures, especially on Oracle and PostgreSQL. Since the beginning of his career, he has specialized in Oracle Technologies and is Oracle Certified Professional 12c and Oracle Certified Expert RAC\/GridInfra. Over time, Daniel has become increasingly interested in open source technologies, becoming \u201cTechnology Leader Open Infrastructure\u201d and PostgreSQL expert. \u00a0Based on community or EnterpriseDB tools, he develops and installs complex high available solutions with PostgreSQL. He is also a certified PostgreSQL Plus 9.0 Professional and a Postgres Advanced Server 9.4 Professional. He is a regular speaker at PostgreSQL conferences in Switzerland and Europe. Today Daniel is also supporting our customers on AWS services such as AWS RDS, database migrations into the cloud, EC2 and automated infrastructure management with AWS SSM (System Manager). 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