mysql set primary key
ALTER TABLE tableName MODIFY COLUMN id INT; /* First you should drop auto increment */
ALTER TABLE tableName DROP PRIMARY KEY; /* Dop primary key */
ALTER TABLE tableName ADD PRIMARY KEY (new_id); /* Set primary key to the new column */
ALTER TABLE tableName MODIFY COLUMN new_id INT AUTO_INCREMENT; /* Set auto increment to the new primary key */MySql get primary keys of table
SELECT COLUMN_NAME
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_SCHEMA = 'Your Database'
AND TABLE_NAME = 'Your Table name'
AND COLUMN_KEY = 'PRI';
SELECT COLUMN_NAME
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_SCHEMA = 'Your Database'
AND TABLE_NAME = 'Your Table name'
AND COLUMN_KEY = 'UNI';what is primary key
Primary Key :
It is unique column in every table in a database
It can ONLY accept;
- nonduplicate values
- cannot be NULL
Foreign Key:
It is a column that comes from a different table and
using Foreign key tables are related each other
It is the primary key of another table
It can be duplicate or null for another table
Unique Key:
Only unique value and also can contain NULLCopyright © 2021 Codeinu
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