GETTING STARTED WITH MYSQL How a database stores information All the data in MySQL is stored in tables, very much in the same way as in a spreadsheet, with information organized into rows and columns. Figure 10-1 shows the database table that you will build later in this chapter, as displayed in phpMyAdmin. Figure 10-1. A database table stores information in rows and columns like in a spreadsheet. Each column has a name (image_id, filename, and caption) indicating what it stores. The rows aren t labeled, but the first column (image_id) contains a unique value known as a primary key, which identifies the. | GETTING STARTED WITH MYSQL How a database stores information All the data in MySQL is stored in tables very much in the same way as in a spreadsheet with information organized into rows and columns. Figure 10-1 shows the database table that you will build later in this chapter as displayed in phpMyAdmin. Record Column Field Primary key Figure 10-1. A database table stores information in rows and columns like in a spreadsheet. Each column has a name image_id filename and caption indicating what it stores. The rows aren t labeled but the first column image_id contains a unique value known as a primary key which identifies the data associated with the row. Each row contains an individual record of related data. The intersection of a row and a column where the data is stored is called a field. For instance the caption field for the third record in Figure 10-1 contains the value The Golden Pavilion in Kyoto and the primary key for that record is 3. The terms field and column are often used interchangeably particularly by phpMyAdmin. A field holds one piece of information for a single record whereas a column contains the same field for all records. How primary keys work Although Figure 10-1 shows image_id as a consecutive sequence from 1 to 8 they re not row numbers. Figure 10-2 shows the same table with the captions sorted in alphabetical order. The field highlighted in Figure 10-1 has moved to the seventh row but it still has the same image_id and filename. 281 CHAPTER 10 Now in the seventh row but imagejd -remains unchanged Download from Wow eBook Figure 10-2. The primary key identifies the row even when the table is sorted in a different order. Although the primary key is rarely displayed it identifies the record and all the data stored in it. Once you know the primary key of a record you can update it delete it or use it to display data in a separate page. Don t worry about how you find the primary key. It s easily done using Structured Query .
