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Tag: mysql

MYSQL Add working days to date

I want to add 5 days to the provided date, but the calculation must skip weekends. I already know how to add 5 days without skipping weekends: SELECT DATE_ADD(`date_field`, INTERVAL 5 DAY) As …

What’s the meaning of RESTRICT in Foreign Keys?

There is 4 cases: (For example I’m talking about ON DELETE) CASCADE: the referencing rows will be deleted automatically along with the referenced ones. SET NULL: the value of referencing record will be set to NULL automatically along with the referenced ones. NO ACTION: There will not be any change in t…

Why should I use EXISTS() function in MySQL?

I have this query: And when I remove that EXISTS() function, still my code works: So why should I write that? What’s its advantage? Answer In short: EXISTS returns when it finds the first result instead of fetching all matching records (so it is more efficient when there are multiple records matching th…

MySQL: How to convert seconds to mm:ss format?

I want to convert seconds to minute : seconds format in sql select statement. At the moment I am using: It works perfectly but it gives me this format of time: hh:mm:ss but I need mm:ss Is it possible to convert seconds into mm:ss format using sql query? Answer If the value is less than an hour, then just do:

Select from two tables with group by date

I have two tables: Table t1: So from this table I want to get count field Id for each day. For this I use next query: It’s work good. So next table is t2. To select data by date from this table I use next query: It’s also work good. So my purpose is merge these two queries into one

PHP Prepared statement bind_param() error

Many people on stackoverflow has had this problem, but i still cannot spot the mistake This is the error: This is the lines of code: Answer After every mysqli or PDO function that COULD return a bad/failed status you must test for that possibility. The error Fatal error: Call to a member function bind_param()…