Databases
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    <p><strong>Store elements in one database field as an array and count using serve-side language after one read.</strong></p> <p>This one is pretty much bad bad bad. Not only is it bad from a design perspective, but every time you want to count, you have to effectively return all elements. The database spends longer reading actual file pages, as well as longer sending the data back to the client. Once it's on client, you then need to parse it, and then get the count. All taken, this can be FAR slower and is a much worse design.</p> <p><strong>Spreading the array in fields and counting the number of fields using SQL COUNT.</strong></p> <p>The best option of the three, if modified. You don't want to spread the array as fields. You really want to spread it out as rows. You want a 1 to many relationship table. This allows the database to do what it's good at, only accessing the minimum amount of required information, and only returning a single number at the end. Much less work involved for everyone here.</p> <p><strong>Storing a field in database which contains an unpdated value of the sum of elements to count.</strong></p> <p>This can mean two different things. The first is that you have a field that you manually update every time you insert/delete. This would be bad, because it's easy to forget, so why do it? While this could be the most performant of all of the options, it also increases risk. The second, would be to have a calculated column store the count for you. This allows sql server to keep track of it for you, and can be a reasonable option for making queries easier, but can negatively impact performance when you otherwise don't want a count if you grab the entire row. Overall, the second of these isn't bad, but is pretty situational for when it's actually good.</p>
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    1. CO+1 and I am thanking you for the detailed answer and the edits. really appreciated. I am reading and understanding
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    2. COPlease to note that in the first approach I will only perform one read. of course it can be a long array. Is it still a bad approach to avoid?
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    3. COI would still say yes, because it is significantly less flexible, and while it's one read, that full read must be done every time. It could also still span several disk pages, and could be the equivalent of more than 1 read. There is no ability for the database to apply various optimizations such as using indexes or only pulling back specific elements that it's asking for if you didn't want to evaluate every one of them.
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