What are indexes? When do you need to create Indexes?
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Answer Posted / radhakrishnan
index : increase the performance of sql statement.
When we create :
1) large number of data in table
2) most of null value in specific column
3) multiple join in sql statement
4) less than 2% of data retrive from table
when we not create :
1) frequently update the table
2) less number of data
Type of Index :
1) clustered index
- primary & unique constaint cretae autoatically for this
index
- only one clustered index per table.
- data sorted physical order
- Eg : book front index
2) non clustered index
- create multiple index per table.
- Eg : book back index
Syntax :
Create index index_name on tablename (column name)
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