MySQL – Add Column to Index
Index is used to access rows of a table with increased performance.
Consider that you are having a large table and has a query in which you fetch the rows based on a column. If the column is not PRIMARY KEY but you use that quite often for filtering the rows, then it is better to add the column to the index.
To add a column to the index of table, following is the syntax of the SQL Query.
ALTER TABLE table_name ADD INDEX index_name (column_name);
Example to add a column to the INDEX in MySQL
Consider the following students
table.
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whose INDEX is as shown below:
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Now we shall add one more column of students
table to the INDEX. Let us say, the column, section
.
Using the syntax mentioned earlier, we prepared the following SQL Query and we shall run it in mysql.
ALTER TABLE students ADD INDEX nameIndex (section);
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The column section
is added to the INDEX with index_name as sectionIndex
.
In future, you may access this particular index with the name sectionIndex
.
Let us verify, if this has been added to the INDEX of the table.
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