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Before we even look at the SQL SELECT command, we must know what motivates the experienced database programmer to pick certain kinds of queries and avoid others. The first motivator is of course performance. We all want our programs to go fast. If you want a fast database program, then you have to think about the hard disk.
The slowest device in a computer is the disk drive. The price of disk reads is so much higher than in-memory operations that there is nothing to gain by optimizing code unless disk reads are optimized first. I often tell my programmers to consider in-memory operations to be "free" when coding, and to concentrate all optimization efforts on reducing disk reads. This approach may gloss over some important truths, but it is an excellent starting point for database beginners.
Optimizing disk reads comes down to writing efficient queries on top of well-designed tables. With that being said, we have one more short note to cover before going into the syntax of the queries.
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The slowest device in a computer is the disk drive. The price of disk reads is so much higher than in-memory operations that there is nothing to gain by optimizing code unless disk reads are optimized first. I often tell my programmers to consider in-memory operations to be "free" when coding, and to concentrate all optimization efforts on reducing disk reads. This approach may gloss over some important truths, but it is an excellent starting point for database beginners.
Optimizing disk reads comes down to writing efficient queries on top of well-designed tables. With that being said, we have one more short note to cover before going into the syntax of the queries.
More...
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