Joins are fundamental concepts in SQL and they are prefer by professionals as they are faster then sub-queries. These 3 easy MySQL examples below are a little effort to let visitors understand difference among Inner join, Left Outer join and Full outer join.
I have the old database in which time was stored as string with AM/PM. One day I required to do some time calculation on that field. I have googled out for convert time string into time with AM/PM in MySQL and found some solution.
Sometime we face the problems for concatenating of group rows column value in a single string. Group_concat() is a function which help us to achieve this.
Saving comma separated values or delimited list in database looks convenient at first but never use them because most and most of the time that’s only a bad idea. I have provided many reasons to avoid them and only one when you can take favour of.
There is no rank function in MySQL actually, whenever you need to query rank from table based on some functionality/criteria in MYSQL. But there are simple queries that can be used to perform the same.
Read the article to create query as well as to know about equivalent query for RANK and DENSE_RANK in MySQL.
We can concatenate multiple MySQL rows into one field using GROUP_CONCAT function in mySQL query. There might be situations when you select multiple values from multiple tables and after all the joins you have got a lot of rows than you would like. We can use`GROUP_CONCAT` to obtain the same result with less numbers of rows.
Get the last inserted ID of a MySQL table is a simple query to obtain the primary key of the record you just inserted to the table. Here I have explained the query using PDO as well as Mysqli.
Also, I have abbreviated few points while using PDO or if you are trying to get the last inserted ID of a MySQL table in PHP using other methods.
With help of the following simple query you can find sum of multiple columns values in a row.
In the `marks` table below we have roll number and marks of each student in physics, chemistry and maths. Now we wish to find sum of marks obtained by each student.
You can easily remove duplicate rows in MySQL and keep just one record for each. I have provided two solutions here, one is simple query and second is using subquery to attain the same
If we try to execute a simple MySQL query or any database query that contains reserved word as a table or column name we come across syntax errors.
We have discuss two options to have Defense from syntax error using a reserved word as a table or column name.