SQL LEFT JOIN
SQL Tutorial » SQL LEFT JOIN
What is a SQL LEFT join?The LEFT JOIN returns all records from the left table (table1), even if there are no matches in the right table.
This means that a left join returns all the values from the left table, plus matched values from the right table or NULL in case of no matching join predicate.
Syntax:
FROM table_1
LEFT JOIN table_2
ON table_1.common_field = table_2.common_field;
Let's look at the Table1 "Customer" table: We will have four columns as: "Customer_ID", "Name", "Age" and "Value_salary"
Customer_ID | Name | Age | Value_Salary |
---|---|---|---|
1 | Kent Ford | 27 | 1900 |
2 | Joveau Pierre | 41 | 2200 |
3 | Anderson Nime | 34 | 1800 |
4 | Martínez Alexandro | 26 | 2700 |
5 | Parker Table | 31 | 1700 |
Table 2 − "Orders" Table is as follows.:
Orders_ID | Date | Customer_ID | Amount |
---|---|---|---|
101 | 2019-10-08 12:14:00 | 1 | 2300 |
102 | 2019-10-08 12:22:00 | 3 | 2400 |
103 | 2019-10-08 12:31:00 | 4 | 1900 |
104 | 2019-10-08 12:37:00 | 4 | 1600 |
105 | 2019-10-08 01:20:00 | 4 | 2000 |
How do I join two tables with LEFT join? - Examples
Now, let us join these two tables Customer and Orders using the LEFT JOIN as follows:
FROM CUSTOMER
LEFT JOIN ORDERS
ON CUSTOMER.Customer_ID = ORDERS.Customer_ID;
Output displayed:
Order_ID | Name | Amount | Date |
---|---|---|---|
1 | Kent Ford | 1900 | 2019-10-08 12:14:00 |
2 | Joveau Pierre | NULL | NULL |
3 | Anderson Nime | 2300 | 2019-10-08 12:22:00 |
4 | Martínez Alexandro | 2200 | 2019-10-08 12:31:00 |
4 | Martínez Alexandro | 2200 | 2019-10-08 12:37:00 |
4 | Martínez Alexandro | 2200 | 2019-10-08 01:20:00 |
5 | Parker Table | NULL | NULL |
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Tags: SQL LEFT JOIN: example, vs right join, select, nultiple tables, vs left outer join, vs inner join, on multiple columns, with where clause, right join, duplicate row,
What is a SQL LEFT join?
Is Left join the same as left outer join?
How do I join two tables with LEFT join?
When to use left join vs Right join?
SQL operators to JOIN tables
Several operators can be used to join tables, such as =, <, >, <>, <=, >=, !=, BETWEEN, LIKE, and NOT; they can all be used to join tables.
SQL JOIN - WHERE clause vs. ON clause
WHERE clause and ON clause are not the same.
WHEREFROM Orders
LEFT JOIN OrderLines ON OrderLines.OrderID=Orders.ID
WHERE Orders.ID = 12345
AND
FROM Orders
LEFT JOIN OrderLines ON OrderLines.OrderID=Orders.ID
AND Orders.ID = 12345
The first will return an order and its lines, if any, for order number 12345. The second will return all orders, but only order 12345 will have any lines associated with it.
SQL LEFT JOIN: example, vs right join, select, nultiple tables, vs left outer join, vs inner join, on multiple columns, with where clause, right join, duplicate row,
What is a SQL LEFT join?
Is Left join the same as left outer join?
How do I join two tables with LEFT join?
When to use left join vs Right join?
SQL LEFT JOIN - sql tutorial
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