mysql - Can i set Unique constraints and Not Null constraints to same …
Nov 30, 2012 · CREATE TABLE TABLE_NAME ( eno NUMBER ,ename VARCHAR2(100) ,address VARCHAR2(2000) ,mobileno NUMBER NOT NULL ,constraint …
MySQL UNIQUE Constraint - W3Schools
The UNIQUE constraint ensures that all values in a column are different. Both the UNIQUE and PRIMARY KEY constraints provide a guarantee for uniqueness for a column or set of …
How to Create Unique Constraint with NULL Columns in SQL
Apr 24, 2024 · By creating a unique constraint with NULL columns, we can ensure that non-NULL values are unique while allowing multiple rows with NULL values. In this article, We will …
sql - How do I add both the UNIQUE and NOT NULL constraints …
Sep 24, 2023 · You can use an in-line constraint for NOT NULL: CREATE TABLE BOOK_STORES ( Store_ID NUMBER(8) , Name VARCHAR2(30) NOT NULL , Contact …
Dealing with MySQL nulls and unique constraint - Medium
Mar 29, 2019 · The first solution that would come to my mind is to add a deleted_at column with type TIMESTAMP and extend a constraint to (name, deleted_at). Let’s try it! ADD deleted_at …
MySQL Constraints - W3Schools
Constraints can be column level or table level. Column level constraints apply to a column, and table level constraints apply to the whole table. The following constraints are commonly used …
Create Unique Constraint with NULL Columns in MySQL
Sep 18, 2024 · The syntax for creating a unique constraint with NULL columns in MySQL involves specifying the UNIQUE keyword during table creation or altering an existing table: CREATE …
mysql - Multi-field unique constraint where we include one or …
Jun 16, 2017 · Suppose I have four columns | x | y | z | w | I would like the following constraint: If w is NULL, then x, y, z must be unique. If w is not NULL, then x, y, w must be unique. Is this …
How to do unique constraint works with NULL value in MySQL
Feb 8, 2017 · If you use a UNIQUE constraint but don't want multiple rows with NULL, declare the columns as NOT NULL and prohibit any row from having NULL. There are ways to implement …
MySQL UNIQUE Constraint
To define a UNIQUE constraint for a column when creating a table, you use the following syntax: ..., column1 datatype UNIQUE, ... In this syntax, you include the UNIQUE keyword in the …