MySQL list keys

Summary: in this tutorial, you will learn how to query index information from a table by using the MySQL

SHOW INDEXES FROM table_name IN database_name;

Code language: SQL (Structured Query Language) (sql)
0 command.

Introduction to MySQL SHOW INDEXES FROM table_name IN database_name; Code language: SQL (Structured Query Language) (sql)0 command

To query the index information of a table, you use the

SHOW INDEXES FROM table_name IN database_name;

Code language: SQL (Structured Query Language) (sql)
0 statement as follows:

SHOW INDEXES FROM table_name;

Code language: SQL (Structured Query Language) (sql)

To get the index of a table, you specify the table name after the

SHOW INDEXES FROM table_name IN database_name;

Code language: SQL (Structured Query Language) (sql)
3 keyword. The statement will return the index information associated with the table in the current database.

You can specify the database name if you are not connected to any database or you want to get the index information of a table in a different database:

SHOW INDEXES FROM table_name IN database_name;

Code language: SQL (Structured Query Language) (sql)

The following query is similar to the one above:

SHOW INDEXES FROM database_name.table_name;

Code language: SQL (Structured Query Language) (sql)

Note that

SHOW INDEXES FROM table_name IN database_name;

Code language: SQL (Structured Query Language) (sql)
4 and

SHOW INDEXES FROM table_name IN database_name;

Code language: SQL (Structured Query Language) (sql)
5 are the synonyms of the

SHOW INDEXES FROM table_name IN database_name;

Code language: SQL (Structured Query Language) (sql)
6,

SHOW INDEXES FROM table_name IN database_name;

Code language: SQL (Structured Query Language) (sql)
7 is the synonym of the

SHOW INDEXES FROM table_name IN database_name;

Code language: SQL (Structured Query Language) (sql)
3, therefore, you can use these synonyms in the

SHOW INDEXES FROM table_name IN database_name;

Code language: SQL (Structured Query Language) (sql)
0 column instead. For example:

SHOW INDEX IN table_name FROM database_name;

Code language: SQL (Structured Query Language) (sql)

Or

SHOW KEYS FROM tablename IN databasename;

Code language: SQL (Structured Query Language) (sql)

The

SHOW INDEXES FROM table_name IN database_name;

Code language: SQL (Structured Query Language) (sql)
0 returns the following information:

table

The name of the table

non_unique

1 if the index can contain duplicates, 0 if it cannot.

key_name

The name of the index. The primary key index always has the name of

SHOW INDEXES FROM database_name.table_name;

Code language: SQL (Structured Query Language) (sql)
1.

seq_in_index

The column sequence number in the index. The first column sequence number starts from 1.

column_name

The column name

collation

Collation represents how the column is sorted in the index.

SHOW INDEXES FROM database_name.table_name;

Code language: SQL (Structured Query Language) (sql)
2 means ascending,

SHOW INDEXES FROM database_name.table_name;

Code language: SQL (Structured Query Language) (sql)
3 means descending, or

SHOW INDEXES FROM database_name.table_name;

Code language: SQL (Structured Query Language) (sql)
4 means not sorted.

cardinality

The cardinality returns an estimated number of unique values in the index.

Note that the higher the cardinality, the greater the chance that the query optimizer uses the index for lookups.

sub_part

The index prefix. It is null if the entire column is indexed. Otherwise, it shows the number of indexed characters in case the column is partially indexed.

packed

indicates how the key is packed; NUL if it is not.

null

SHOW INDEXES FROM database_name.table_name;

Code language: SQL (Structured Query Language) (sql)
5 if the column may contain NULL values and blank if it does not.

index_type

represents the index method used such as

SHOW INDEXES FROM database_name.table_name;

Code language: SQL (Structured Query Language) (sql)
6,

SHOW INDEXES FROM database_name.table_name;

Code language: SQL (Structured Query Language) (sql)
7,

SHOW INDEXES FROM database_name.table_name;

Code language: SQL (Structured Query Language) (sql)
8, or

SHOW INDEXES FROM database_name.table_name;

Code language: SQL (Structured Query Language) (sql)
9.

comment

The information about the index not described in its own column.

index_comment

shows the comment for the index specified when you create the index with the

SHOW INDEX IN table_name FROM database_name;

Code language: SQL (Structured Query Language) (sql)
0 attribute.

visible

Whether the index is visible or invisible to the query optimizer or not;

SHOW INDEXES FROM database_name.table_name;

Code language: SQL (Structured Query Language) (sql)
5 if it is,

SHOW INDEX IN table_name FROM database_name;

Code language: SQL (Structured Query Language) (sql)
2 if not.

expression

If the index uses an expression rather than column or column prefix value, the expression indicates the expression for the key part and also the

SHOW INDEX IN table_name FROM database_name;

Code language: SQL (Structured Query Language) (sql)
3 column is NULL.

Filter index information

To filter index information, you use a

SHOW INDEX IN table_name FROM database_name;

Code language: SQL (Structured Query Language) (sql)
4 clause as follows:

SHOW INDEXES FROM table_name WHERE condition;

Code language: SQL (Structured Query Language) (sql)

You can use any information returned by the

SHOW INDEXES FROM table_name IN database_name;

Code language: SQL (Structured Query Language) (sql)
0 statement to filter the index information. For example, the following statement returns only the invisible indexes of a table:

SHOW INDEXES FROM table_name WHERE VISIBLE = 'NO';

Code language: SQL (Structured Query Language) (sql)

MySQL SHOW INDEXES FROM table_name IN database_name; (adsbygoogle = window.adsbygoogle || []).push({}); Code language: SQL (Structured Query Language) (sql)0 examples

We will create a new table named

SHOW INDEX IN table_name FROM database_name;

Code language: SQL (Structured Query Language) (sql)
7 to demonstrate the

SHOW INDEXES FROM table_name IN database_name;

Code language: SQL (Structured Query Language) (sql)
0 command:

CREATE TABLE contacts( contact_id INT AUTO_INCREMENT, first_name VARCHAR(100) NOT NULL, last_name VARCHAR(100) NOT NULL, email VARCHAR(100), phone VARCHAR(20), PRIMARY KEY(contact_id), UNIQUE(email), INDEX phone(phone) INVISIBLE, INDEX name(first_name, last_name) comment 'By first name and/or last name' );

Code language: SQL (Structured Query Language) (sql)

The following command returns all index information from the

SHOW INDEX IN table_name FROM database_name;

Code language: SQL (Structured Query Language) (sql)
7 table:

SHOW INDEXES FROM contacts;

Code language: SQL (Structured Query Language) (sql)

The output is:

MySQL list keys
MySQL list keys

To get the invisible indexes of the

SHOW INDEX IN table_name FROM database_name;

Code language: SQL (Structured Query Language) (sql)
7 table, you add a

SHOW INDEX IN table_name FROM database_name;

Code language: SQL (Structured Query Language) (sql)
4 clause as follows:

SHOW INDEXES FROM contacts WHERE visible = 'NO';

Code language: SQL (Structured Query Language) (sql)

Here is the output:

MySQL list keys
MySQL list keys

In this tutorial, you have learned how to use the MySQL

SHOW INDEXES FROM table_name IN database_name;

Code language: SQL (Structured Query Language) (sql)
0 statement to get the index information of a table.

What is the list of keys in MySQL?

The 5 keys supported by MySQL are Primary Key, Unique Key, Candidate Key, Foreign Key, and Super Key. You learned how to create a table to define and also how to alter the table for primary and unique keys.

How to list all foreign keys in MySQL?

To see all FKs in your table: USE '<yourschema>'; SELECT i. TABLE_NAME, i. CONSTRAINT_TYPE, i. CONSTRAINT_NAME, k. ... .
To see all the tables and FKs in your schema: USE '<yourschema>'; SELECT i. TABLE_NAME, i. CONSTRAINT_TYPE, i. ... .
To see all the FKs in your database: SELECT i. TABLE_SCHEMA, i. TABLE_NAME, i..

How to get list of indexes in MySQL?

To see indexes for all tables within a specific schema you can use the STATISTICS table from INFORMATION_SCHEMA: SELECT DISTINCT TABLE_NAME, INDEX_NAME FROM INFORMATION_SCHEMA. STATISTICS WHERE TABLE_SCHEMA = 'your_schema'; Removing the where clause will show you all indexes in all schemas.

How to show primary key in MySQL?

MySQL primary key is a single or combination of the field, which is used to identify each record in a table uniquely. If the column contains primary key constraints, then it cannot be null or empty..
CREATE TABLE table_name(.
col1 datatype PRIMARY KEY,.
col2 datatype,.