Apparently it depends on the Windows installation language, how the date function or %DATE% environment variable is formatted. So here is a very ugly hack to get a julian date (YYYYMMDDHHiiss) in a Windows batch script, independent off system locale settings:
- @echo off
- FOR /F "usebackq tokens=1-10 delims=+|NOW():- " %%a IN (`mysql -e "SELECT NOW();" -u root -ptest`) DO set datetime=%%a%%b%%c%%d%%e%%f
- echo %datetime%
Notice that this requires MySQL. If you do not like to use your MySQL root code, you can create a new user with absolutely no rights granted.
But again, this solution is stupid, I hope you will never need it or use it. I just thought I would share, since it was driving my co-worker crazy, and we ended up using it to name a MySQL dump.
Sometimes a parent table have more than one table with multiple references to a field in the parent table. Then the question is how to count references from more than one table in a single query. I have found 5 different ways to achieve this result, and therefore I have run a few tests, to see which was better.
To test this I made this small PHP script, that creates a parent table and child table. Then a loop populates the tables with 1,000 parent rows, approximately 15 children of type 1 and approximately 75 children of type 2. This is done before each query, to make sure that all queries have the same conditions.
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Today I tried to execute the SQL
mysql> ALTER TABLE parent_child ADD FOREIGN KEY (parent_id)
REFERENCES parent(id) ON DELETE CASCADE;
in MySQL, and got the error
Can't create table 'db.#sql-aa1_1' (errno: 150)
I tried to look up error number 150 on the internet, but found many reasons why error no. 150 could occur; none was my case. Common mistakes that causes this error are:
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