CREATE TABLE ArtistMember (

  user_ID INT PRIMARY KEY

);

​

CREATE TABLE FollowerMember (

  user_ID INT PRIMARY KEY

);

​

CREATE TABLE pledge (

    pledge_ID            INT CONSTRAINT  XPKPledge PRIMARY KEY,

    pledge_endDate       DATE NULL,

    pledge_startDate     DATE NULL,

    pledge_amount        DECIMAL(9,2) NULL  CONSTRAINT  Currency_1322638346 CHECK (pledge_amount >= 0),

    artist_userID        INT NOT NULL CONSTRAINT gets REFERENCES ArtistMember (user_ID),

    follower_userID      INT NOT NULL CONSTRAINT makes REFERENCES FollowerMember (user_ID)

);

​

INSERT INTO ArtistMember VALUES ( 85275 );

INSERT INTO FollowerMember VALUES( 88128 );

INSERT INTO pledge VALUES(

  559,

  NULL,              -- Use NULL and not 'NULL'

  DATE '2016-02-01', -- Use a Date literal and not a string literal

  3850,

  85275,

  88128

);