Translate the following question to SQL: What is the average balance in checking accounts?

Schema: CREATE TABLE ACCOUNTS (
    custid BIGINT NOT NULL  PRIMARY KEY,
    name VARCHAR(64) NOT NULL,
    UNIQUE (custid)
);

CREATE TABLE SAVINGS (
    custid BIGINT NOT NULL  PRIMARY KEY,
    balance FLOAT NOT NULL,
    UNIQUE (custid),
    FOREIGN KEY (custid) REFERENCES ACCOUNTS(custid)
);

CREATE TABLE CHECKING (
    custid BIGINT NOT NULL  PRIMARY KEY,
    balance FLOAT NOT NULL,
    UNIQUE (custid),
    FOREIGN KEY (custid) REFERENCES ACCOUNTS(custid),
    CREATE TABLE CHECKING (
);
user
SELECT avg(balance) FROM checking
assistant