Choosing the correct data type is a simple and yet important task. Specifying the wrong data type may result in not only wasted disk space but also poor performance. To choose the correct data type, you need to fully understand your data and their possible values and usage. Table 3.4 offers a checklist for data type selection.
Unnecessary casting can cost performance. Try to define the variables in the SQL procedures with the same data types as the underlining table columns.
REAL, FLOAT, and DOUBLE are imprecise data types where rounding may occur. You should not use these data types for storing precise data, such as primary key values or currency data.