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SQL Tutorial
SQL HOME SQL Intro SQL Syntax SQL Select SQL Select Distinct SQL Where SQL Order By SQL And SQL Or SQL Not SQL Insert Into SQL Null Values SQL Update SQL Delete SQL Select Top SQL Aggregate Functions SQL Min() SQL Max() SQL Count() SQL Sum() SQL Avg() SQL Like SQL Wildcards SQL In SQL Between SQL Aliases SQL Joins SQL Inner Join SQL Left Join SQL Right Join SQL Full Join SQL Self Join SQL Union SQL Union All SQL Group By SQL Having SQL Exists SQL Any SQL All SQL Select Into SQL Insert Into Select SQL Case SQL Null Functions SQL Stored Procedures SQL Comments SQL Operators
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Numeric Functions: ABS ACOS ASIN ATAN ATAN2 AVG CEIL CEILING COS COT COUNT DEGREES DIV EXP FLOOR GREATEST LEAST LN LOG LOG10 LOG2 MAX MIN MOD PI POW POWER RADIANS RAND ROUND SIGN SIN SQRT SUM TAN TRUNCATE
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SQL INDEX Keyword
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CREATE INDEX
The CREATE INDEX command is used to
create indexes in tables (allows duplicate values).
Indexes are used to retrieve data from the database very fast. The users cannot see the indexes, they are just used to speed up searches/queries.
The following SQL creates an index named "idx_lastname" on the "LastName" column in the "Persons" table:
CREATE INDEX idx_lastname
ON Persons (LastName);
If you want to create an index on a combination of columns, you can list the column names within the parentheses, separated by commas:
CREATE INDEX idx_pname
ON Persons (LastName, FirstName); Note:** The syntax for creating indexes varies among different databases. Therefore: Check the syntax for creating indexes in your database.
Note: Updating a table with indexes takes more time than updating a table without (because the indexes also need an update). So, only create indexes on columns that will be frequently searched against.
DROP INDEX
The DROP INDEX command is used to delete an
index in a table.
MS Access:
DROP INDEX index_name ON table_name;
SQL Server:
DROP INDEX table_name.index_name;
DB2/Oracle:
DROP INDEX index_name;
MySQL:
ALTER TABLE *table_name *DROP INDEX index_name;
❮ Previous ❮ SQL Keywords Reference Next ❯
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