Details
Critical Description
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' )
------------
| PLAN |
------------
| DELETE ROWS |
| CLIENT PARALLEL 1-WAY FULL SCAN OVER SALES |
| SERVER FILTER BY FIRST KEY ONLY |
EXPLAIN DELETE FROM SALES;
------------
| PLAN |
------------
| DELETE ROWS |
| CLIENT PARALLEL 1-WAY FULL SCAN OVER SALES |
| SERVER FILTER BY FIRST KEY ONLY |