sql server create constraint
ALTER TABLE my_table ALTER COLUMN [Name] VARCHAR(50) NOT NULL;
ALTER TABLE my_table ADD CONSTRAINT UQ__Constrai UNIQUE (ID);
ALTER TABLE my_table ADD PRIMARY KEY (ID);
-- Get constraints names
SELECT CONSTRAINT_NAME,
TABLE_SCHEMA ,
TABLE_NAME,
CONSTRAINT_TYPE
FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS
WHERE TABLE_NAME='my_table';
ALTER TABLE my_table DROP CONSTRAINT PK__Constrai__xxxxx;constraints in sql
RULES ABOUT THE COLUMNS IN TABLE
NOT NULL # Ensures a column cannot have a NULL value
UNIQUE # Ensures all values in a column are unique
PRIMARY KEY # Identifies a record in a table, is NOT NULL & UNIQUE
FOREIGN KEY # References a unique record from another table
CHECK # Ensures all column values satisfy a condition
DEFAULT # Set a default value for a column if none is entered
INDEX # Quick way of retrieving records from databaseCopyright © 2021 Codeinu
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