DELETE using Subqueries

DELETE's using a subquery deletes all the rows in the table igonoring any condition set by the where clause, here's an example -

CREATE TABLE IF NOT EXISTS CUSTOMER (
CUSTOMER_ID INTEGER NOT NULL,
CUSTOMER_NAME VARCHAR NOT NULL,
CUSTOMER_CITY VARCHAR
CONSTRAINT pk PRIMARY KEY (CUSTOMER_ID,CUSTOMER_NAME)
);

CREATE TABLE IF NOT EXISTS SALES (
SALE_ID INTEGER NOT NULL,
CUSTOMER_NAME VARCHAR NOT NULL,
SALE_AMOUNT INTEGER
CONSTRAINT pk PRIMARY KEY (SALE_ID,CUSTOMER_NAME)
);

UPSERT INTO CUSTOMER VALUES(1,'MSFT','SEATTLE');
UPSERT INTO CUSTOMER VALUES(2,'AMZN','SEATTLE');
UPSERT INTO CUSTOMER VALUES(3,'APPL','CUPERTINO');
UPSERT INTO CUSTOMER VALUES(4,'TSLA','PALO ALTO');

UPSERT INTO SALES VALUES(1,'MSFT',1000);
UPSERT INTO SALES VALUES(2,'AMZN',1000);
UPSERT INTO SALES VALUES(3,'APPL',1000);
UPSERT INTO SALES VALUES(4,'TSLA',1000);

DELETE FROM SALES WHERE CUSTOMER_NAME IN (SELECT CUSTOMER_NAME FROM CUSTOMER WHERE CUSTOMER_CITY = 'SEATTLE' ) => Deletes all the rows

EXPLAIN DELETE FROM SALES WHERE CUSTOMER_NAME IN (SELECT CUSTOMER_NAME FROM CUSTOMER WHERE CUSTOMER_CITY = 'SEATTLE' )
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EXPLAIN DELETE FROM SALES;
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