SQL

SQL Syntax of LEFT JOIN

SELECT columns
FROM table1
LEFT JOIN table2
ON table1.column_name = table2.column_name;

SQL LEFT JOIN

SELECT Customers.customer_id, Customers.first_name, Orders.amount
FROM Customers
LEFT JOIN Orders
ON Customers.customer_id = Orders.customer;

LEFT JOIN

SELECT
	pka,
	c1,
	pkb,
	c2
FROM
	A
LEFT JOIN B ON pka = fka;
Code language: SQL (Structured Query Language) (sql)
/* https://www.postgresqltutorial.com/postgresql-tutorial/postgresql-left-join/ */

left join sql

#LEFT JOIN: Return all rows from the left table, even if there are no matches in the right
#table 
syntax->SELECT column_name(s)
FROM table_name1
LEFT JOIN table_name2
ON table_name1.column_name=table_name2.column_name 
////example/////
SELECT Persons.LastName, Persons.FirstName, Orders.OrderNo
FROM Persons
LEFT JOIN Orders
ON Persons.P_Id=Orders.P_Id
ORDER BY Persons.LastName 

Left join

SELECT *
FROM Table_A A
LEFT JOIN Table_B B
ON A.col = B.col;

right join

RIGHT JOIN: Matching part from both
table and unmatching part from right table.

left join

SELECT table1.column1, table2.column2...
FROM table1
RIGHT JOIN table2
ON table1.common_field = table2.common_field;

left join

Matching part from both table and unmatching part from left table.

left join

123SELECT columns  FROM table_A  LEFT JOIN table_B ON join_conditionsXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

left join

You need a first lookup for the values that exist in table1, so make a map using an object:

var maps = {};
for (var i = 0; i < table1.length; i++) {
  maps[table1[i].attr4] = 1;
}

Then you can loop throught the items in table2 and filter them:

var result = [];
for (i = 0; i < table2.length; i++) {
  if (!(table2[i].attr3 in map)) {
    result.push(table2[i]);
  }
}

Left join

SQL> SELECT  ID, NAME, AMOUNT, DATE
   FROM CUSTOMERS
   LEFT JOIN ORDERS
   ON CUSTOMERS.ID = ORDERS.CUSTOMER_ID;