user21002
0
Q:

make primary key in sql


CREATE TABLE table_name
(
   Column1 datatype,		// column1 and datatype
   Column2 datatype,		// column2 and datatype
   Column3 datatype,		// column3 and datatype
  
   PRIMARY KEY (Column1);	// column1 is the primary key
); 
6

CREATE TABLE Persons
(

    ID int NOT NULL PRIMARY KEY,

   
LastName varchar(255) NOT NULL,

   
FirstName varchar(255),

   
Age int

); 
1
-- NOTE: this is for SQL-Oracle specifically

-- example:
SELECT cols.table_name, cols.column_name, cols.position, cons.status, cons.owner
FROM all_constraints cons, all_cons_columns cols
WHERE cols.table_name = 'CUSTOMERS' 
AND cons.constraint_type = 'P'
AND cons.constraint_name = cols.constraint_name
AND cons.owner = cols.owner;

-- syntax:
SELECT cols.table_name, cols.column_name, cols.position, cons.status, cons.owner
FROM all_constraints cons, all_cons_columns cols
WHERE cols.table_name = '<table-name>' -- Replace <table-name> with your table-name
AND cons.constraint_type = 'P'
AND cons.constraint_name = cols.constraint_name
AND cons.owner = cols.owner;
1

CREATE TABLE Persons
(

    ID int NOT NULL,

   
LastName varchar(255) NOT NULL,

   
FirstName varchar(255),

   
Age int,

   
PRIMARY KEY (ID)

); 
0
The PRIMARY KEY constraint uniquely identifies each record in a table.
Primary keys must contain UNIQUE values, and cannot contain NULL values. 
A table can have only ONE primary key; and in the table, this primary key can consist of single or multiple columns (fields).
-1

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