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MySQL is an open source database management system developed by MySQL AB |
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A primary key is a single column or multiple columns defined to have unique values that can be used as row identifications. |
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A foreign key is a single column or multiple columns defined to have values that can be mapped to a primary key in another table. |
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An index is a single column or multiple columns defined to have values pre-sorted to speed up data retrieval speed. |
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Join is data retrieval operation that combines rows from multiple tables under certain matching conditions to form a single row. |
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A transaction is a logical unit of work requested by a user to be applied to the database objects. MySQL server introduces the transaction concept to allow users to group one or more SQL statements into a single transaction, so that the effects of all the SQL statements in a transaction can be either all committed (applied to the database) or all rolled back (undone from the database). |
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Commit is a way to terminate a transaction with all database changes to be saved permanently to the database server. |
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MyISAM is a storage engine used as the default storage engine for MySQL database. MyISAM is based on the ISAM (Indexed Sequential Access Method) concept and offers fast data storage and retrieval. But it is not transaction safe. |
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sUse DISTINCT in the query, such as SELECT DISTINCT user_firstname FROM users; You can also ask for a number of distinct values by saying SELECT COUNT (DISTINCT user_firstname) FROM users. |
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When you’re not deleting by row ID. Such as in DELETE FROM table_question ORDER BY timestamp LIMIT 1. This will delete the most recently posted question in the table techinterviews_com_questions. |
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The first is, naturally, the character count. The second is byte count. For the Latin characters the numbers are the same, but they’re not the same for Unicode and other encodings. |