Every table must be identified with a unique key or the Primary Key. Primary Key uniquely identifies each record in the table. It makes searching of record faster.
A Primary Key cannot contain a NULL values and must be unique in every record.
Different DBMS have different implementations to set the primary keys, so let’s see each of them below.
SQL PRIMARY KEY Syntax
Besides creating the database from the DBMS software like Oracle, MyQL, Microsoft Access etc. We can also create database with the query language. It is as simple as writing a SELECT, INSERT, UPDATE, DELETE Statement.
Creating a database using query language is very useful if for example you deploy your application to a computer that doesn’t have a database yet.
We can create a new database with the following syntax
SQL Create Database Syntax
The FULL JOIN keyword will return all rows from both tables that you specified. The same as other JOINS, FULL JOIN has the same syntax as show below.
The RIGHT JOIN keyword works the same way as LEFT JOIN keyword except that it returns all rows from the right table. This means that even there is no matching record from the left join the rows will still show from the second table.
There are times when you want to retrieve all data from one table even there is no matching record from both tables. Unlike SQL INNER Join, SQL LEFT Join will still show you the result from the left table or the first table. SQL INNER Join as discussed in the previous chapter will only show records that match on both tables based on the column you specified.
SQL INNER JOIN is almost the same as the normal join. But the INNER JOIN will only list those rows which have at least one matching value from both tables.
SQL INNER JOIN Syntax