Validation table for data tables

I'm new to db design and have a couple of problems.

I have a job title field in 3 data tables and need to use a validation table to limit the range of values. My question: Do I need to create a separate validation table for each of the data tables, or can I use only one and link it to all the 3 data tables?

Another question: Is it better to have an optional Health Professional field set to Null for a Trainees table, or would you recommend to have a validation table with two values:ye开发者_StackOverflow社区s,no.

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Do I need to create a separate validation table for each of the data tables, or can I use only one and link it to all the 3 data tables?

Use one. Each of the other three tables can set a foreign key reference to it.

Is it better to have an optional Health Professional field set to Null for a Trainees table, or would you recommend to have a validation table with two values:yes,no.

Neither. I think this is a better approach.

• Use a Boolean column.
• Declare it to be NOT NULL.
• Set a default value. Use the most common for your app, either DEFAULT TRUE or DEFAULT FALSE.

If you can design without NULLs, you're usually better off.

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Validate all string values before insert data into the db, if you're using php consider using:

$cc = "1234567891234567";
$max_size = 16;
$string_size = strlen($cc);
if($cc > $max_size )
{
    echo "your string must be < than $max_size characters";
}