CREATE TABLE ACCOUNTS (
    custid      BIGINT      NOT NULL PRIMARY KEY,
    name        VARCHAR(64) NOT NULL
)

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

CREATE TABLE CHECKING (
    custid      BIGINT      NOT NULL PRIMARY KEY,
    balance        FLOAT       NOT NULL,
    FOREIGN KEY (custid) REFERENCES ACCOUNTS (custid)
)
SELECT avg(balance) FROM checking
Find the average checking balance.