A2 SSD — SQL

SQL

SQL is a non-procedural language (no branching or iteration) where the result wanted is described, not the method used to obtain the result.

SQL can:

• define a database
• add, delete and update data
• manipulate and summarise data

Used in commercial relational DBMS. Not usually case sensitive.

It accepts one or more relations as input and produces a single relation as output.

When choosing data types you should:

• Minimise the disk space used
• Consider if the datatype is suitable for future needs as it is very costly to change a data type
• A fixed length string may be preferred when the number of characters needed is small
• float and real should only be used when the precision of a decimal is insufficient