April 2026
Intermediate
1009 pages
34h 15m
English
Content preview from PHP and MySQL
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17.6 Special Features
That's SQL in a nutshell. You can now perform almost all standard tasks on the web. This section shows some more advanced techniques.
17.6.1 Relational Database Design
Until now, our setup was relatively simple: One table contained all the data. However, you may have noticed that some information is repeated in the table. For example, you can see that the names and email addresses of the two guestbook entrants are entered again and again. This is called redundancy. It would be more efficient if this data were stored in a different table. Each of the entries has a primary key. This "foreign" primary key of the person making the entry would then be used in table entry. For this reason, this is called a foreign key
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