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 …
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 …
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 …
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 …
How do I create a unique constraint that also allows nulls?
Apr 20, 2009 · CREATE UNIQUE NONCLUSTERED INDEX idx_yourcolumn_notnull ON YourTable(yourcolumn) WHERE yourcolumn IS NOT NULL; In earlier versions, you can resort …
sql - Allow null in unique column - Stack Overflow
Drop the email column from the table. Put it in a new table where it can be NOT NULL and UNIQUE: CREATE TABLE CompanyEmail ( CompanyUniqueID INT NOT NULL PRIMARY …
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 …
SQL | Constraints - GeeksforGeeks
Jan 30, 2025 · UNIQUE Constraint. The UNIQUE constraint ensures that all values in a column are distinct across all rows in a table. Unlike the PRIMARY KEY, which requires uniqueness …
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 …
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