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How do indexes help in speeding up searching for data based on specific criteria?
If there's a table with 6 columns and none of them are indexed, the program has to check all table rows.
Indexing involves creating another separate table with just two columns, the id and the column you want indexed.
What I don't understand, is how does that help the application do faster searches? It doesn't read the entire 6 column table, but it still has to read the entire 2 column table, right? Which has the same number of rows...
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When a data is inserted, a corresponding row is written to the index, and when a row is deleted, its index row is taken out. This keeps the data and searching index always in sync making the lookup very fast and read-time efficient.
Every time you add an index, it writes on the indexed table become slower as it has to balance more B-tree structures every time a record comes in .
An index is used to speed up data search and SQL query performance. The database indexes reduce the number of data pages that have to be read in order to find the specific record. The biggest challenge with indexing is to determine the right ones for each table.
Indexes help faster data retrieval from the databases . Basically, it speeds up the select queries and where clause. But at the same time, it degraded the performance of INSERT and UPDATE queries.
It functions a lot like an index in a book. We don't read the entire index to find the entry we want, and once we find the entry, we don't keep reading the index for other instances of that same entry. Once we find the entry, we don't have to read the entire book, just jump to the entry we want. These operations are in normal table lookups and indexing saves us time much in the same way a book index would.
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