{"id":10548,"date":"2022-09-24T02:18:35","date_gmt":"2022-09-23T20:48:35","guid":{"rendered":"https:\/\/jassweb.com\/solved\/solved-having-clause-trouble\/"},"modified":"2022-09-24T02:18:35","modified_gmt":"2022-09-23T20:48:35","slug":"solved-having-clause-trouble","status":"publish","type":"post","link":"https:\/\/jassweb.com\/solved\/solved-having-clause-trouble\/","title":{"rendered":"[Solved] Having clause trouble"},"content":{"rendered":"<p> [ad_1]<br \/>\n<\/p>\n<div id=\"answer-13783155\" class=\"answer js-answer accepted-answer js-accepted-answer\" data-answerid=\"13783155\" data-parentid=\"13783075\" data-score=\"1\" data-position-on-page=\"1\" data-highest-scored=\"1\" data-question-has-accepted-highest-score=\"1\" itemprop=\"acceptedAnswer\" itemscope itemtype=\"https:\/\/schema.org\/Answer\">\n<div class=\"post-layout\">\n<div class=\"votecell post-layout--left\"><\/div>\n<div class=\"answercell post-layout--right\">\n<div class=\"s-prose js-post-body\" itemprop=\"text\">\n<p>This and all your other questions smell like you&#8217;re doing some test or course. Shouldn&#8217;t it be time that you at least <em>attempt<\/em> to solve one of these questions yourself?<\/p>\n<pre><code>select\n  d.dname,\n  AVG(salary)\nfrom\n  department d\n  inner join employee e on e.Dno = d.dnumber\ngroup by\n  d.dname\nhaving\n  avg(salary) &gt; 33000\n<\/code><\/pre>\n<p>First of all, I use d and e as aliases for Department and Employee. You can specify aliases after the table name in the query. You can use them to prefix field names, but you don&#8217;t have to if that field exists in only one table.<\/p>\n<p>Let&#8217;s continue with the inner join. There&#8217;s a relation between the tables. It looks like department.dnumber contains the department number. Also, employee.Dno contains the department number of the employees. By joining the table, you combine the data. The query will return a row for each department and for all employees. The information of the department is duplicated for each employee that is returned.  <\/p>\n<p>The the <a rel=\"nofollow noopener\" target=\"_blank\" href=\"http:\/\/en.wikipedia.org\/wiki\/Aggregate_function\">aggregation<\/a>. SQL knows a number of <em>aggregate<\/em> functions. If you select a field or a couple of fields to &#8216;group&#8217; by, you can use other fields to &#8216;aggregate&#8217; over. So in this case, I group by department name. I earlier said it would the return the department information multiple times, one time for each employee of the department. Now, this step <em>groups<\/em> that information again. It returns the department name only one time, and aggregates the employee information. In this case, I use AVG to calculate the avarage salary, but you could also use <code>SUM(salary)<\/code> to get the total salary of all employees in the department, or <code>COUNT(*)<\/code> to count the number of employees per department. <\/p>\n<\/p><\/div>\n<div class=\"mt24\"><\/div>\n<\/div>\n<p>            <span class=\"d-none\" itemprop=\"commentCount\">8<\/span> <\/p><\/div>\n<\/div>\n<p>[ad_2]<\/p>\n<p>solved Having clause trouble <\/p>\n","protected":false},"excerpt":{"rendered":"<p>[ad_1] This and all your other questions smell like you&#8217;re doing some test or course. Shouldn&#8217;t it be time that you at least attempt to solve one of these questions yourself? select d.dname, AVG(salary) from department d inner join employee e on e.Dno = d.dnumber group by d.dname having avg(salary) &gt; 33000 First of all, &#8230; <a title=\"[Solved] Having clause trouble\" class=\"read-more\" href=\"https:\/\/jassweb.com\/solved\/solved-having-clause-trouble\/\" aria-label=\"More on [Solved] Having clause trouble\">Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[320],"tags":[340],"class_list":["post-10548","post","type-post","status-publish","format-standard","hentry","category-solved","tag-mysql"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v26.5 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>[Solved] Having clause trouble - JassWeb<\/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:\/\/jassweb.com\/solved\/solved-having-clause-trouble\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"[Solved] Having clause trouble - JassWeb\" \/>\n<meta property=\"og:description\" content=\"[ad_1] This and all your other questions smell like you&#8217;re doing some test or course. 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