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Quiz

## Instruction

Yes, that's right! Now, let's take a closer look at various constraints.

## Exercise

A forex agency needs a simple table to keep track of the currency exchanges they perform.

Create a table called exchange with the following columns:

• id - an integer which is the primary key,
• currency_from - exactly three characters,
• currency_to - exactly three characters,
• quantity - a decimal field of 10 digits, 2 out of which are after the decimal point,
• rate - a decimal field of 6 digits, 2 out of which are after the decimal point,
• time - a field with date and time.

Mind the following requirements:

• No column can be a NULL.
• The columns quantity and rate must be greater than zero.
• If no value is provided, the default quantity is 100.00.

### Stuck? Here's a hint!

We discussed constraints in Part 5. Take a look back to refresh your memory.