I'm using SQL Fiddle, and I'm unable to run a simple query (SELECT * FROM CUSTOMER;) after building my schema with the code below. The only error I get is "Oops! Something went wrong. Try it again and if this keeps happening, email admin@sqlfiddle.com about it." Before I email SQL Fiddle, I figured I'd check if there's something wrong in my schema that's causing the issue.
CREATE TABLE CUSTOMER (
C_CUSTOMER_ID INTEGER(3) NOT NULL UNIQUE,
C_LNAME VARCHAR(20) NOT NULL,
C_FNAME VARCHAR(15) NOT NULL,
C_ADDRESS VARCHAR(50) NOT NULL,
C_CITY VARCHAR(25) NOT NULL,
C_STATE CHAR(2) NOT NULL,
C_ZIP CHAR(5) NOT NULL,
C_HOME_PHONE CHAR(10) NOT NULL,
C_MOB_PHONE CHAR(10),
C_OTH_PHONE CHAR(10),
PRIMARY KEY (C_CUSTOMER_ID));
CREATE TABLE ORDER_TABLE (
ORDER_ID INTEGER(5) NOT NULL UNIQUE,
ORDER_DATE DATETIME NOT NULL,
ORDER_NOTES VARCHAR(250) NOT NULL,
C_CUSTOMER_ID INTEGER,
PRIMARY KEY (ORDER_ID),
FOREIGN KEY (C_CUSTOMER_ID) REFERENCES CUSTOMER(C_CUSTOMER_ID));
CREATE TABLE DONUT (
DONUT_ID INTEGER(3) NOT NULL UNIQUE,
DONUT_NAME VARCHAR(15) NOT NULL,
DONUT_DESCR VARCHAR(50) NOT NULL,
DONUT_PRICE DECIMAL(2,2) NOT NULL,
PRIMARY KEY (DONUT_ID));
CREATE TABLE LINE_ITEMS (
DONUT_ID INTEGER NOT NULL,
ORDER_ID INTEGER NOT NULL,
QUANTITY INTEGER(3) NOT NULL,
PRIMARY KEY (DONUT_ID, ORDER_ID),
FOREIGN KEY (DONUT_ID) REFERENCES DONUT(DONUT_ID),
FOREIGN KEY (ORDER_ID) REFERENCES ORDER_TABLE(ORDER_ID));
SQL Fiddle has had issues for several years (see link), and hasn't had an update to the source they have on GitHub for over 2 years. Also, looking at all sqlfiddler tags at SO, many people are having similar issues.
I tried your code on RexTester and it works without issues so I would imagine it's another issue with SQL Fiddle and not your code.