Sql join vs left outer join

Id ORDER BY TotalAmount This will list all customers, whether they placed any order or not. In SQL , a join is used to compare and combine — literally join — and return specific rows of data from two or more tables in a database. An inner join finds and returns matching data from tables, while an outer join finds and returns matching data and some dissimilar data from tables. Inner Join Vs Outer Join : Get Ready to Explore the Exact Differences Between Inner and Outer Join.

A join clause is used to combine records or to manipulate the records from two or more tables through a join condition.

In this excerpt from SQL Queries for Mere Mortals: A Hands-On Guide to Data Manipulation in SQL , John L. Hernandez discuss the LEFT OUTER JOIN vs. RIGHT OUTER JOIN and offer tips on how to use each of them in SQL statements. Venn diagrams illustrate the difference in output rows for special cases of inner vs outer join. What is the difference between INNER JOIN. This is because the LEFT OUTER Join is doing more work than an INNER Join BEFORE sending the back.

The Inner Join looks for all records where the ON statement is true (So when it creates a new table, it only puts in records that match the m.SubID = a.SubID).

Right Outer Join is similar to Left Outer Join (Right replaces Left everywhere) 3) Full Outer Join Contains of both Left and Right outer joins. Frankly speaking, in Sql Server there is no difference between LEFT JOIN and LEFT OUTER JOIN. They produce the same result and also the same performance. Let us prove with examples that there is no difference between LEFT JOIN and LEFT OUTER JOIN. A left outer join (also known as a left join ) retains all of the rows of the left table, regardless of whether there is a row that matches on the right table.

The SQL above will give us the result set shown below. The good news is that when it comes to right outer joins or, its twin, the left outer join , there isn’t much of a difference to learn. When it comes to the right vs left outer join debate, it is more about point-of-view. Want to know the difference between Outer Apply and Left Join.

For the same query if i use Outer Apply, query output will be faster but in some DBs Outer Apply takes log period for returning details. You can learn more about left and right outer joins in this article, for now just understand that when a LEFT OUTER JOIN is use all rows for the table in the FROM clause are included in the result, even if a match isn’t found with the other table. When a match isn’t foun then a NULL is place in the column.

Oracle, Sybase, SQL Server and PostgreSQL as well. I just came across APPLY in SQL and loved how it solves query problems for so many cases, Many of the tables I was using left join to get the result, I was able to get in outer apply. Except above mentioned scenarios JOIN can be a good choice instead of APPLY for it’s simplicity of syntax and to match all rows at once instead of invoking right input every time for each row of left input , as APPLY invokes.

Performance of APPLY vs JOIN.

In different scenarios, performance of JOIN and APPLY are different. Use of the left join or left outer join statement in the SQL environment will refer to the exact same statement. This in essence means that there is no difference as to the result expected whether a left join is used or a left outer join is used.

The result will be similar, unless the environment is in the Microsoft SQL server. SQL OUTER JOIN – left outer join. SQL left outer join is also known as SQL left join.

Suppose, we want to join two tables: A and B. The PostgreSQL LEFT JOIN joins two tables and fetches rows based on a condition, which is matching in both tables and the unmatched rows will also be available from the table written before the JOIN clause. In MySQL CROSS JOIN , INNER JOIN and JOIN are the same. In the standar and semantically, a CROSS JOIN is an INNER JOIN without an ON clause, so you get every combination of rows between tables. You have examples of all semantic types of join on. In practice, in MySQL, we tend to only write JOIN and LEFT JOIN.

RIGHT JOIN performs a join starting with the second (right-most) table and then any matching first ( left -most) table records.