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What is indexing in mysql and how do we create indexing in
mysql
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Answer Posted / ramya
Two type of indexing
Spatial indexes (created using SPATIAL INDEX):
1.Available only for MyISAM tables. Specifying a
SPATIAL INDEX for other storage engines results in an error.
2.Indexed columns must be NOT NULL.
3.In MySQL 5.0, the full width of each column is
indexed by default, but column prefix lengths are allowed.
However, as of MySQL 5.0.40, the length is not displayed in
SHOW CREATE TABLE output. mysqldump uses that statement. As
of that version, if a table with SPATIAL indexes containing
prefixed columns is dumped and reloaded, the index is
created with no prefixes. (The full column width of each
column is indexed.)
Nonspatial indexes (created with INDEX, UNIQUE, or PRIMARY KEY):
1.Allowed for any storage engine that supports spatial
columns except ARCHIVE.
2.Columns can be NULL unless the index is a primary key.
3.For each spatial column in a non-SPATIAL index except
POINT columns, a column prefix length must be specified.
(This is the same requirement as for indexed BLOB columns.)
The prefix length is given in bytes.
4.The index type for a non-SPATIAL index depends on the
storage engine. Currently, B-tree is used.
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