Search engine Z uses only a subset of the SQL language, and does not perform some of the basic functions of a database. For example, it probably doesn't support JOIN operations, the DISTINCT argument, the GROUP BY command, the HAVING clause. These are all generic features of the SQL language. And when records are updated (changed), it must rebuild the search index in a time-consuming batch operation. In between index rebuilds - which may occur only once a day - searches match the old stale data, not the new data. A true relational database (of which Texis is one) never allows the indexes to get "out of sync" with the data.
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