The syntax and logic of SQL

As mentioned earlier, SQL is an easy to use and understand language capable of many different types of operations. Like all languages, it is based on interpreting command strings that are inserted with an expected syntax, with specific statements corresponding to one and only possible operation. SQL's main statements can be of many types. Let's take a look at the most important ones:

• SELECT statement: SELECT is the most common SQL command. Its purpose is to allow the database to be searched, showing the specified attributes from the records that satisfy (optionally) a specific condition; for example:

  SELECT color, shape FROM objects 

  This statement shows the color and shape attributes of all the records from the objects table. SQL also allows for a wildcard – in this case, the character * – to make general selections:

  SELECT * FROM objects 

• This statement will return all the records from objects table, showing all the attributes...