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Mysql add column index after11/21/2023 ![]() Hence, it is best to treat identifiers as case-sensitive. The names or identifiers (database names, table names, column names, etc.) are case-sensitive in some systems, but not in other systems. For clarity, they are shown in uppercase. The SQL keywords and commands are NOT case-sensitive. A table is made up of columns (or fields) and rows ( records). Each database consists of one or more tables. SHOW WARNINGS - Show the warnings of the previous statement An Example for the Beginners (But NOT for the dummies)Ī MySQL database server contains many databases (or schemas). , columnNValue) - Insert on selected Columns VALUES ( column1Value, column2Value.) - Insert on all Columns SHOW CREATE TABLE tableName - Show the CREATE TABLE statement for this tableName - Row-Level Modify a table, e.g., ADD COLUMN and DROP COLUMNĪLTER TABLE tableName ADD columnDefinitionĪLTER TABLE tableName ADD FOREIGN KEY ( columnNmae) REFERENCES tableName ( columnNmae) ALTER TABLE tableName DROP FOREIGN KEY constraintName SHOW TABLES - Show all the tables in the default databaseĭESCRIBE|DESC tableName - Describe the details for a tableĪLTER TABLE tableName. įOREIGN KEY ( columnNmae) REFERENCES tableName ( columnNmae) SHOW CREATE DATABASE databaseName - Show the CREATE DATABASE statement - Table-LevelĬolumnName columnType columnAttribute. SELECT DATABASE() - Show the default database USE databaseName - Set the default (current) database SHOW DATABASES - Show all the databases in this server Database-LevelĭROP DATABASE databaseName - Delete the database (irrecoverable!)ĭROP DATABASE IF EXISTS databaseName - Delete if it existsĬREATE DATABASE databaseName - Create a new databaseĬREATE DATABASE IF NOT EXISTS databaseName - Create only if it does not exists Summary of MySQL Commands Used in this Tutorialįor detailed syntax, check MySQL manual "SQL Statement Syntax". Print " MySQL: MySQl index has been Removed.Read " How to Install MySQL and Get Started" on how to install, customize, and get started with MySQL. $result = mysql_query("DROP INDEX xyz ON emp_dtl",$con) Print " MySQL: MySQl index has been Created. $result = mysql_query("CREATE INDEX xyz ON emp_dtl(id)",$con) $result = mysql_query("select * from emp_dtl") The following is an example of a MySQL create and drop of an index in PHP: The fourth query "DROP INDEX xyz ON emp_dtl" removes the index of the emp_dtl table.Įxample of a MySQL create and drop MySQL index in PHP You can use a "DROP INDEX" statement to drop an index. The third query "SHOW INDEX FROM emp_dtl" shows the description of the emp_dtl table index. The second MySQL query "CREATE INDEX xyz ON emp_dtl(id)" creates an index with the name xyz for table emp_dtl on id columns. ![]() In the following query image, the first query "select * from emp_dtl" simply shows all records of the emp_dtl table. The syntax of the "CREATE INDEX" statement is as follows: CREATE INDEX index_name If you do not specify "asc" or "desc", then "asc" is the default same as the "order by" keyword (which is also able to sort columns in "asc" or "desc" order). You can also specify "ASC" and "DESC" keywords with a column name to indicate whether you want the "index" stored in ascending or descending order. You can also use "UNIQUE" keywords to specify that an "index" has only unique values. To create an index, write the table name and column names after the "on" clause. You must have used a "CREATE INDEX" statement to create an index for one or more columns of a table. ![]() The indexes are used to speed up database queries and also used by a database engine to locate records very quickly. In addition, you may want to create "indexes" for other columns that are frequently used in joins or search conditions. MySQL automatically creates an index for primary key, foreign key, and unique constraints. An "index" can improve the speed of operation in a table.
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