Structured Query Language
In the SQL SELECT Statement we can also group data upon certain conditions, the GROUP BY condition can only be applied if we have redundant values in at least one column upon which we can group things.
If every column of each row has unique value then the GROUP BY clause will not group any thing together and will not give proper results.
The GROUP BY clause also requires the use of an aggregate function, which does some mathematical calculations upon the grouped data.
Whenever you want to retrieve data from your table, there are times that you don’t want to pull all the information. You can retrieve data from the database by using the WHERE clause to filter data based on your criteria.
The WHERE clause in SQL is used to filter out data or to simply select specific data to perform the desired operation.
The WHERE clause can be used in SELECT, UPDATE, and DELETE statement. It is needed to filter what data to select, update, or delete.
One of the problems that I encounter when I started programming is on how to save record to a database.
I feel I need to share the knowledge that I gained within 10 years of my experience so that other programmer who would like to learn will benefit on this tutorial.
SQL stands for Structured Query Language and is the standard for accessing and or manipulating a database.
This tutorial will use the ISO standard so that you can apply the code that I will provided here.
When you insert data into your table you may need to update it sometimes. Not so often we inserted or updated a wrong data. That’s why there is a Delete statement.
To delete some record from the database tables we use the SQL Delete statement, the Delete Statement deletes the data row from the table which meets the condition specified in the where clause.
The delete command has the following syntax:
When you insert record to your table there are some cases that you need to modify the data. Or you may want to update it to the latest record.
The SQL update is there to help us modify the existing values of the table, the SQL update statement used the same column name as insert statement and the new value that you want to placed and the table name to update the data successfully.
The syntax of SQL update statement is as follows:
SQL Insert command is used to save record into a database in a specific table.
The SQL Insert command has the following syntax:
The select command is used to retrieve data from the tables.
Consider the following table:
Users:
SQL is not syntax strict like JavaScript which mean to say that in SQL uppercases and lowercases don’t matter as long as you have spelled them correctly.
For example: