| Q1: | How is it that I can enter numbers such as a person's Social Security number in fields defined as character fields? |
| A1: | Numeric values are still alphanumeric , which are allowed in character data types. Typically, the only data stored as numeric values are values used in computations . However, it may be helpful for some to define all numeric fields with a numeric data type to help control the data entered in that field. |
| Q2: | I still do not understand the difference between constant-length and varying-length data types. Can you explain? |
| A2: | Say you have an individual's last name defined as a constant data type with a length of 20 bytes. Suppose the individual's name is Smith. When the data is inserted into the table, 20 bytes are taken, 5 for the name and 15 for the extra spaces (remember that this is a constant-length data type). If you use a varying-length data type with a length of 20 and inserted Smith, only 5 bytes of space are taken. |
| Q3: | Are there limits on the lengths of data types? |
| A3: | Yes, there are limits on the lengths of data types and they do vary among the various implementations . |