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SQL CREATE Command

Intro

Use the CREATE command to create a table, schema, or database


CREATE SCHEMA payroll

-- or

CREATE TABLE payroll.timecards
  (sin# NUMERIC(9) PRIMARY KEY,
  starttime DATETIME,
  endtime DATETIME)

Add a primary key to two columns


CREATE TABLE rainchecks
  (check# NUMERIC(6) PRIMARY KEY,
  cus_name VARCHAR(30) NOT NULL,
  phone NUMERIC(10) CHECK(phone > 0),  -- any clause that can be written in a WHERE 
  raindate DATETIME)
  
CREATE TABLE raincheck_details
  (check# NUMERIC(6) FOREIGN KEY REFERENCES rainchecks(check#),
  item char(3),
  price NUMERIC(10,2),
  PRIMARY KEY(check#, item))

ALTER


-- add a column
ALTER TABLE rainchecks
  ADD email VARCHAR(50)
  
-- change a column type  
ALTER TABLE rainchecks
  ALTER COLUMN cus_name VARCHAR(40)
  
-- delete a column  
ALTER TABLE rainchecks
  DROP COLUMN email
  
-- add a constraint (use a good name)
ALTER TABLE rainchecks
  ADD CONSTRAINT need_price
  CHECK (price > 0)
  
-- delete a constraint
ALTER TABLE rainchecks
  DROP CONSTRAINT need_price