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    <p>Gaps in sequences are <strong>inevitable</strong> when dealing with <strong>transactional</strong> databases.</p> <p>First, you cannot use <code>SELECT max(id)+1</code> because it may give the same <code>id</code> to 2 transactions which execute at the same time. This means you have to use database native auto-increment column (MySQL, SQLite) or database sequence (PostgreSQL, MSSQL, Oracle) to obtain next available <code>id</code>.</p> <p>But even using auto-increment sequence does NOT solve this problem. Imagine that you have 2 database connections that started 2 parallel transactions almost at the same time. First one acquired some <code>id</code> from auto-increment sequence and it became previously used value +1. One nanosecond later, second transaction acquired next <code>id</code>, which is now +2. Now imagine that first transaction rolled back for some reason (encountered error, your code decided to abort it, program crashed - you name it). After that, second transaction committed with <code>id</code> +2, creating a gap in <code>id</code> numbering.</p> <p>But what if number of such parallel transactions was more than 2? You cannot predict, and you also cannot tell currently running transactions to reuse <code>id</code>s that were abandoned.</p> <p>It is theoretically possible to reuse abandoned ids. However, in practice it is prohibitively expensive on database, and creates more problems when multiple sessions try to do the same thing.</p> <p><strong>TDLR:</strong> stop fighting it, gaps in used ids are perfectly normal.</p>
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    1. POHow to use Linq to Sql as a Serial Number Generator to avoid Gaps?
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Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

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