View allAll Photos Tagged sql
Here are the collection of SQL indexes Interview Questions or Database indexing interview questions
1. What is an index?
Index is a data structure which is created on one or more columns of the table. In most of the cases, the indexes are structured as B tree. When index is created on a column of a table, it actually creates a lookup table with column and a pointer to the memory address where a row with this column is actually stored. Therefore when we query a table with column in WHERE clause, the parser first checks if this column is part of index, and if there is a index lookup table for it. If yes, then it checks for the memory address where the record is stored. It then directly jumps to that memory address and returns the result to the user. That is why index scan or if a column has index, then it retrieves the data faster.
2. What kind of data structure is an index?
In most of the cases, B-Tree data structure is used to store the indexes. This is because of the time efficiency of B-Trees. In other words, B-trees are traversed, searched, inserted, deleted and updated in logarithmic time. In addition, B-Tree data are always sorted and stored. Hence it makes searching and inserting the data in known fraction of time. The data values stored in B-trees are balanced – all the values smaller than a particular node can be found at the left of the node and the values greater than the node value are found at the right of the node.
www.tutorialcup.com/interview/sql-interview-questions/ind...
Microsoft® SQL Server Express 2017 – Microsoft® SQL Server Express for small data based Web applications and small phones with up to 10 GB with &...