Left Outer Join. Gleich wie inner join dann für alle Zeilen in der linken Tabelle, dass nicht alles, was diese Ausgabe mit NULL-Werten für die richtigen Spalten der Tabelle. Right Outer Join. Gleich wie inner join dann für alle Zeilen in der rechten Tabelle, die nicht alles, was diese Ausgabe mit NULL-Werten für den linken Spalten der Tabelle. Full Outer Join. Gleich wie inner join, dann. SQL: Unterschied zwischen LEFT JOIN, RIGHT JOIN und INNER JOIN unter Access Anhand von Code-Beispielen, ohne viel Erklärung, soll hier kurz der Unterschied der JOINs unter Access aufgezeigt werden. Die Ausgangstabellen INNER JOIN gets all records that are common between both tables based on the supplied ON clause. LEFT JOIN gets all records from the LEFT linked and the related record from the right table,but if you have selected some columns from the RIGHT table, if there is no related records, these columns will contain NULL Darstellung von INNER JOIN und OUTER JOINs in Form von Mengendiagrammen: Die farbigen Flächen entsprechen der Ergebnismenge des jeweiligen JOINs der Mengen A und B. Die Ergebnismenge des INNER JOINs ist die Schnittmenge von A und B (dunkelblau). Die Ergebnismenge eines OUTER JOINs umfasst die Schnittmengen zwischen A und B (dunkelblau) sowie die Restmenge (hellblau) von A (LEFT JOIN), B. Differences between inner join & outer join. The following Venn diagram clearly shows the difference between each join type. There are three kinds of joins in SQL Server, inner, outer and cross. The outer join is further divided as left, right & full. INNER JOIN: Returns only matched row
Hauptunterschied: Joins in SQL werden ausgeführt, um die Daten von zwei verschiedenen Tabellen zu kombinieren. Ein Inner Join ist eine Bedingung, die zu den Zeilen führt, die die wo -Klausel in allen Tabellen erfüllen. Ein äußerer Join ist eine Bedingung, die dazu führt, dass die Zeilen die wo -Klausel in mindestens einer der Tabellen erfüllen . It returns the combined tuple between two or more tables. It returns the combined tuple from a specified table even join condition will fail. 2. Used clause INNER JOIN and JOIN. Used clause LEFT OUTER JOIN, RIGHT OUTER JOIN, FULL OUTER JOIN, etc. 3. When any attributes are not common then it will return nothing INNER JOIN vs LEFT JOIN INNER JOIN vs LEFT JOIN? Actually, that is not the question at all. You'll use INNER JOIN when you want to return only records having pair on both sides, and you'll use LEFT JOIN when you need all records from the left table, no matter if they have pair in the right table or not
Difference between Inner Join vs Left join. For demonstration purpose let's create tables and let's call it as - tClass and tStudent tClass table structure. tStudent table structure. Inner join. Inner join matches the common records in two tables joined. Here in the above example we have ClassID in tclass table and ClassID in tstudent table. Below query is used to. Venn diagrams illustrate the difference in output rows for special cases of inner vs outer join.If no nulls or duplicate rows are input (so we can take a table to be a set of row-valued values & use normal math equality) then left & right circles hold output tables/sets of left & right join.But if nulls or duplicate rows are input then it is so difficult to explain just what the circles are.
left_df - Dataframe1 right_df- Dataframe2. on− Columns (names) to join on.Must be found in both the left and right DataFrame objects. how - type of join needs to be performed - 'left', 'right', 'outer', 'inner', Default is inner join. The data frames must have same column names on which the merging happens An outer join is used to return results by combining rows from two or more tables. But unlike an inner join, the outer join will return every row from one specified table, even if the join condition fails. Take the phone directory example above Left Join vs Left Outer Join In SQL, joins are used for the combination of records coming from different sets of data. The join can either be an inner join or an outer join. An inner join returns records which have matches in both tables as opposed to an outer join which is the opposite of the inner Definition of Outer Join. Unlike in Inner Join, only those tuples are output that has same attribute values in both the compared table; Outer Join outputs all the tuples of both the table. Outer Join is of three types Left Outer Join, Right Outer Join, and Full Outer Join. Let us understand them one by one. First, let us take Left Outer Join
SELECT column-names FROM table-name1 LEFT OUTER JOIN table-name2 ON column-name1 = column-name2 WHERE condition ORDER; Id: OrderDate: OrderNumber: CustomerId: TotalAmount: CUSTOMER; Id: FirstName: LastName: City: Country: Phone: SQL LEFT JOIN Example. Problem: List all customers and the total amount they spent irrespective whether they placed any orders or not. SELECT OrderNumber, TotalAmount. In MySQL CROSS JOIN, INNER JOIN and JOIN are the same. In the standard, 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 Wikipedia. In practice, in MySQL, we tend to only write JOIN and LEFT JOIN Per fare ciò basta sostituire nella query che abbiamo visto in precedenza alla clausola INNER JOIN la clausola LEFT OUTER JOIN. SELECT D.IdDipendente,D.Nome,D.Cognome,A.NomeArea FROM dbo.Dipendenti D LEFT OUTER JOIN dbo.Aree A ON A.IdArea = D.IdArea. In questo caso il risultato è il seguente The types of outer joins that might be supported are left, right, full, or nested outer joins; outer joins in which the column names in the ON clause do not have the same order as their respective table names in the OUTER JOIN clause; inner joins in conjunction with outer joins; and outer joins using any ODBC comparison operator. If the SQL_OJ_CAPABILITIES information type returns 0, no outer.
Inner join. 다음 쿼리로 Inner-Join해서 두 테이블의 교집합을 얻습니다. select * from a INNER JOIN b on a.a = b.b; select a.*, b.* from a, b where a.a = b.b; a | b --+-- 3 | 3 4 | 4. Left outer join. Left-Outer-Join은 A에 있는 모든 행과 B에 함께 있는 행을 얻습니다 Buy full Sql Server course from here https://www.questpond.com/learn-sql-server-step-by-step/cid9 For more such videos visit http://www.questpond.com For mor.. Inner Joins; Outer Join; Inner Joins. There are 3 types of inner joins: Theta join; Natural join; EQUI join; Theta Join . A theta join allows one to join two tables based on the condition that is represented by theta. Theta joins can work with all comparison operators. In most cases, the theta join is referred to as inner join. The theta join is the most basic type of JOIN. It will return all.
As expected, by using a LEFT OUTER JOIN instead of the previous INNER JOIN, we're getting the best of both worlds: We're not skipping any books records (such as Hamlet) simply because the language_id value is null for that record, yet for all records where language_id exists, we get the nicely formatted language name obtained from our languages table 1. Monat kostenlos. Exklusive Serien, Filme & Live TV auf Joyn PLUS+. Exklusive Serien, Filme & Live TV auf joyn.de. Jetzt 1. Monat kostenlos testen Inner join and left outer join are only different in the situation where one of the involved tables does not contain any suitable record which meets the join conditions. With an inner join (table 1 inner join table 2), no record is included in the result set in this case. However, this means that the corresponding record from tables 1 is not. Inner Join returns records that have matching values in both tables: Let's see what the output is using the above example: SELECT * FROM BOYS INNER JOIN MESSI ON BOYS.id = MESSI.id; OUTPUT: As I mentioned above, the inner join gives the intersection of two tables, i.e. rows which are common in both the tables. 2. RIGHT (Outer) JOIN in SQ
JOIN t2 on t1.ID = t2.ID means show only records where the same ID value exists in both tables. LEFT JOIN is same as LEFT OUTER JOIN and means to show all records from left table (i.e. the one that precedes in SQL statement) regardless of the existance of matching records in the right table 3 thoughts on Inner Join vs. Left Outer Join vs. Right Outer Join vs. Full Outer Join Examples ravishankar choudhary says: November 21, 2012 at 4:52 pm thank you.. Reply; Brett Hinton says: February 24, 2014 at 6:38 pm Thanks for a concise explanation outlining the differences between the different types of joins. I feel like I have a much better grasp of each one and when it would. • The join_type parameter specifies INNER, LEFT, RIGHT, or FULL outer join. The default join type is INNER. • The search_condition is a valid restriction, subject to the rules for the WHERE clause. The search condition must not include aggregate functions or subselects. Think of an outer join is as the union of two SELECT statements: the first query returns rows that fulfill the join.
INNER JOIN; LEFT/RIGHT JOIN; FULL OUTER JOIN; Syntax . Datenbanksysteme unterstützen verschiedene Schreibweisen für Joins, die sich zum einen in ihrer Anwendbarkeit und zum anderen in der Lesbarkeit unterscheiden. implizite Schreibweise: SELECT X. a, X. b, Y. a, Y. b, c FROM X, Y. explizite Schreibweise: SELECT X. a, X. b, Y. a, Y. b, c FROM X JOIN Y. Zunächst fällt auf, dass die Spalten a. Bei OUTER JOINs handelt es sich um spezielle Abfragen über mehrere Datenbanktabellen hinweg. Man unterscheidet zwischen LEFT OUTER JOINs, RIGHT OUTER JOINs und FULL OUTER JOINs. Jeder dieser JOIN-Typen zeichnet sich gegenüber dem INNER JOIN durch eine größere Ergebnismenge aus. Doch worin genau unterscheiden sich die einzelnen Typen. Bei diesem join werden alle Zeilen aus der Tabelle A mit der Tabelle B zusammengeführt, wo es keine gleichen Elemente gibt. Es entspricht also auch dem left outer join wo der inner join entfernt wurde
It be good to think back on the old ways, since the names arrive from long forgotten history. In the past you would have something like this select <fields> from table1, table2 where table1.field = table2.field That would give you all rows that ma.. Outer join is again classified into 3 types: Left Outer Join, Right Outer Join, and Full Outer Join. These are explained as following below. Left Outer Join: Left Outer Join returns all the rows from the table on the left and columns of the table on the right is null padded. Left Outer Join retrieves all the rows from both the tables that. SQL provides more than one kind of joins such as inner join, left join, right join, full join, etc, but now we ill focus on inner join in SQL. The inner join links two (or more) tables by a relationship between two columns. Whenever you use the inner join clause, you normally think about the intersection between both tables (in case you have two). To understand the concept of inner join in SQL. Hash joins are used for many types of set-matching operations: inner join; left, right, and full outer join; left and right semi-join; intersection; union; and difference. Darüber hinaus können mit einer Variante des Hashjoins Duplikate entfernt und Gruppierungen vorgenommen werden, z.B. SUM(salary) GROUP BY department. Moreover, a variant of the hash join can do duplicate removal and.
An outer join can be a left, right, or full outer join. An inner join discards any rows where the join condition is not met, but an outer joins maintains some or all of the unmatched rows. For an outer join, a specified WHERE clause is applied after the join is performed and eliminates all rows that do not satisfy the WHERE clause. Applying a WHERE clause to an outer join can sometimes defeat. Before we get into the practical example, let us see the visual representation of the SQL Server Inner Join, Full Outer Join, Left Outer Join, Right Outer Join, Self Join, and Cross Join for better understanding
An SQL join clause - corresponding to a join operation in relational algebra - combines columns from one or more tables in a relational database.It creates a set that can be saved as a table or used as it is. A JOIN is a means for combining columns from one (self-join) or more tables by using values common to each. ANSI-standard SQL specifies five types of JOIN: INNER, LEFT OUTER, RIGHT OUTER. Natural join or Inner Join: To keep only rows that match from the data frames, specify the argument all=FALSE. Full outer join or Outer Join:To keep all rows from both data frames, specify all=TRUE. Left outer join or Left Join:To include all the rows of your data frame x and only those from y that match, specify x=TRUE Left JOIN (Video) Right JOIN (Video) Full JOIN (Video) SQL | JOIN (Cartesian Join, Self Join) This article is contributed by Harsh Agarwal.If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to firstname.lastname@example.org. See your article appearing on the GeeksforGeeks main page and help other Geeks . Un inner join -utilizando cualquiera de las sintaxis de consulta equivalente- te entrega la intersección de ambas tablas, es decir, las filas que ambas tablas tienen en común. select * from a INNER JOIN b on a.a = b.b; select a.*, b.* from a, b where a.a = b.b; a | b --+-- 3 | 3 4 | 4 Left outer join
Join. The join prefix joins the loaded table with an existing named table or the last previously created data table.. Syntax: [inner | outer | left | right ] Join [ (tablename )]( loadstatement | selectstatement )The join is a natural join made over all the common fields. The join statement may be preceded by one of the prefixes inner, outer, left or right In this query, T1 is the left table and T2 is the right table. The query compares each row in the T1 table with rows in the T2 table.. If a pair of rows from both T1 and T2 tables satisfy the join predicate, the query combines column values from rows in both tables and includes this row in the result set.. In case a row in the T1 table does not have any matching row in the T2 table, the query. An inner join is a merge operation between two data frame which seeks to only return the records which matched between the two data frames. This is in contrast to a left join , which will return all records from one table (plus any matches) and an outer join which returns everything from both sides Inner Join Vs Outer Join SQL . Both the Inner and Outer Joins are used to combine data from two or more tables and get the single table result. Here the join condition is being used to perform the query that specifies the way in which the data from each table is matched to another table. Here the aim of performing a join on two database tables. Das kartesische Produkt CROSS JOIN, den inneren Verbund in der Form des natürlichen Verbund NATURAL JOIN und anderer Varianten, sowie; den äußeren Verbund in den Formen LEFT OUTER JOIN, RIGHT OUTER JOIN und FULL OUTER JOIN. Als Spezialfall kann man auch einen Verbund einer Tabelle mit sich selbst bilden, dies wird als Self Join bezeichnet
The key difference between a left outer join, and a right outer join is that in a left outer join it's the table in the FROM clause whose all rows are returned. Whereas, in a right outer join we are returning all rows from the table specified in the join clause. See you in the next lesson. If you liked this article I would encourage you to check out my online courses. I have many listed here. Unlike INNER JOIN and LEFT OUTER JOIN, with CROSS JOIN, you don't need to specify a join condition, because SQLite doesn't need it for the CROSS JOIN. The SQLite will result in logical results set by combining all the values from the first table with all the values from the second table. For example, if you selected a column from the first table (colA) and another column from the second table. SQL RIGHT JOIN What is a RIGHT JOIN in SQL? A RIGHT JOIN performs a join starting with the second (right-most) table and then any matching first (left-most) table records. RIGHT JOIN and RIGHT OUTER JOIN are the same INNER join and OUTER join will give you results differently, so you can't replace an INNER join with an OUTER join as it will change your business logic itself. So, if you are the one! who feel changing the join will improve performance then you have to be cautious about this. Instead of changing the joins you have to look into other factors. Check whether indexes are present on the join.
. Why use a FULL OUTER JOIN vs LEFT JOIN or RIGHT JOIN vs an INNER JOIN? To help understand, Let's think about the different questions they are asking. FULL OUTER join: How many friends and connections do my Facebook. Le outer join. A differenza delle inner join, le outer join selezionano i risultati anche in assenza di una corrispondenza su entrambe le tabelle. Più precisamente è possibile definire in MySQL due tipi di outer join, cioè: LEFT JOIN: estrae tutti i valori della tabella a sinistra anche se non hanno corrispondenza nella tabella a destra Note: The INNER JOIN keyword selects all rows from both tables as long as there is a match between the columns. If there are records in the Orders table that do not have matches in Customers, these orders will not be shown! The following SQL statement selects all orders with customer and shipper information INNER JOIN - ruft Daten ab, wenn sie in beiden Tabellen vorhanden sind. OUTER JOIN sind von 3 Arten: LEFT OUTER JOIN - holt Daten, wenn sie in der linken Tabelle vorhanden sind. RIGHT OUTER JOIN - RIGHT OUTER JOIN Daten ab, wenn sie in der rechten Tabelle vorhanden sind Similar to the INNER JOIN clause, the LEFT JOIN clause is an optional clause of the SELECT statement. You use the LEFT JOIN clause to query data from multiple related tables. Suppose we have two tables: A and B. A has m and f columns. B has n and f columns. To perform join between A and B using LEFT JOIN clause, you use the following statement
Der Left Join (auch Left Outer Join genannt) erstellt eine so genannte linke Inklusionsverknüpfung. Diese schließt alle Datensätze aus der ersten (linken) Tabelle ein, auch wenn keine entsprechenden Werte für die Datensätze in der zweiten (rechten) Tabelle existieren. Die zu vergleichenden Spalten müssen explizit Angegeben werden An INNER JOIN will only return matched rows if a row in table A matches many rows in table B the table A row will be repeated with each table B row and vice versa. A FULL OUTER JOIN will return everything an inner join does and return all unmatched rows from each table
Although the question title mentions inner joins, it appears to me that you are asking about when to use a left outer join vs. a right outer join. A LEFT OUTER JOIN is essentially the same thing as a RIGHT OUTER JOIN, and you can use the former in.. In above code we are doing a Left Join. Here the left table is COURSE. So it will return all rows from the course table not depends STUDENT table course_id field. If the course_id field value is in the COURSE table but not in the STUDENT table then in the row course_name and course_desc fields will show and student_name and student_city fields will show NULL. Here the output will be the total.
There are two queries, one which uses INNER JOIN and other query which is same but with LEFT OUTER JOIN.Then it is not same. Its totally different. Both the query will return different result. You cant compare INNER JOIN and OUTER JOIN in terms of Performance. The are two different tools offered by SQL to do different things. They work differently The LEFT OUTER join will retrieve all rows from the table on the left of the join whether they match or not. In the subsequent INNER JOIN, obviously if something doesn't match up, you will lose.. The following join types are the Standard join types in Power BI and SQL. Inner Join: Returns the rows present in both Left and right table only if there is a match.Otherwise, it returns zero records. Full Outer Join: It returns all the rows present in both the Left and right table.; Left Outer Join: It returns all the rows present in the Left table and matching rows from the right table (if any)
. Mit LEFT OUTER JOIN werden die Zeilen in der linken Tabelle beibehalten, sodass Sie alle Kunden sehen, auch diejenigen, für die keine Rechnungen vorliegen. Using the LEFT OUTER JOIN preserves the rows in the left table so that you see all customers, even those who do not have invoices INNER JOIN - RIGHT JOIN - LEFT JOIN. Nicht verstanden habe ich hingegen diese Join-Arten: RIGHT OUTER JOIN - LEFT OUTER JOIN. Doch, hast du. Das OUTER ist einfach nur optional. Was noch fehlt ist der FULL OUTER JOIN. Da werden einfach beide Seiten falls nötig mit NULL ergänzt und nicht nur eine wie bei LEFT/RIGHT Full outer-join flavor. A full outer-join combines the effect of applying both left and right outer-joins. Whenever records in the joined tables don't match, the result set will have null values for every column of the table that lacks a matching row. For those records that do match, a single row will be produced in the result set, containing. The CROSS APPLY operator is semantically similar to INNER JOIN operator. It retrieves those records from the table valued function and the table being joined, where it finds matching rows between the two. On the other hand, OUTER APPLY retrieves all the records from both the table valued function and the table, irrespective of the match Outer Join; Cross Join; Outer Joins are again divided as. Left Join or Left Outer Join; Right Join or Right Outer Join; Full join or Full Outer Join; Let's understand Join types with examples and the differences between them. Read More: Different Types of SQL Keys. 1.Employee Table (tblEmployee) 2.Department table (tblDepartment) Inner Joins:
FROM Table_S INNER JOIN Table_RR ON Table_S.Id = Table_RR.s_Id LEFT OUTER JOIN Table_R LEFT OUTER JOIN Table_FBT INNER JOIN Table_RF ON Table_FBT.Id = Table_RF.FBT_Id ON Table_R.Id = Table_RF.R_Id ON Table_RR.RF_Id = Table_RF.Id WHERE (Table_RF.FBT_Id = N'eac0b83b-be74-429c-ae30-1fae1d861e6c') AND (Table_RF.FT = 1) AND (YEAR(Table_R.EventDate) = 2017) AND (Table_R.O_Id = N'a28fab7b-49f1-40b5. Oracle supports inner join, left join, right join, full outer join and cross join. Note that you can join a table to itself to query hierarchical data using an inner join, left join, or right join. This kind of join is known as self-join. Setting up sample tables. We will create two new tables with the same structure for the demonstration There's not much difference between a left join join and a right join in SQL. Both are outer joins, meaning the result includes all rows from one of the joined tables, even if a given row has no match in the other joined table. But the difference.
Representación de INNER JOIN y OUTER JOIN con diagramas de conjuntos: las áreas coloreadas representan el conjunto de resultados del JOIN a partir de los conjuntos A y B. El INNER JOIN muestra como resultado la intersección de A y B (azul oscuro). El conjunto de resultados de un OUTER JOIN incluye la intersección entre A y B (azul oscuro) y el resto (azul claro) de A (LEFT OUTER JOIN), B. A natural join is one where the tables being joined are being joined on columns with the same name in both tables. Few RDBMS systems support natural joins without specifying the join condition (Oracle is one that does for example), so while joinin.. . Finally, if your situation is that every inquiry_id in the inquiry table always has at least one matching row in the inquiry_event table then there will be no difference between the results of using INNER JOIN and [LEFT] OUTER JOIN LEFT JOIN table 3 INNER JOIN Table 4. ON table3.column = table4.column. ON. table3.column = table1.column Friday, July 20, 2007 5:45 PM. Answers text/html 7/20/2007 7:42:05 PM Arnie Rowland 0. 0. Sign in to vote. My regrets if I came off 'too strong'. Yes, it will work as you have presented the code. If you examine the execution plan, you will see that both INNER JOINs occur, and then there is. SQL LEFT JOIN Keyword. The LEFT JOIN keyword returns all records from the left table (table1), and the matched records from the right table (table2). The result is NULL from the right side, if there is no match. LEFT JOIN Synta
What about inner joins? Now that we've gone over full joins, we can contrast those with the inner join. The difference between an inner join and a full join is that an inner join will return only the rows that actually match based on the join predicate - which in this case is employee.empID = location.empID. Once again, this is best illustrated via an example Joins in SQL are performed to combine the data of two different tables. An Inner Join is a condition, that results the rows, which satisfy the 'where' clause in all the tables; whereas an Outer Join is a condition that results those rows, which satisfy the 'where' clause in at least one of the tables
In short Inner Join= 3 LEft Outer Join=3+0 Right Outer Join= 3+1. Do check from your end. Amit S says: February 12, 2019 at 7:36 pm Yes.You are absolutely right..It was typo and i have corrected that mistakeThanks for lovely suggestions!!! Sharath says: February 17, 2019 at 10:00 am Nice tutorial can send me the joins and sub queries materials and scenario based interview questions . Amit. Left vs Right Join. When dealing with SQL, joins is a common name that will pop up every now and then. The join clause helps in the combination of records from different tables in a data set. The join in effect creates a table that can either be used as it is or rolled out with others based on the common columns in the two tables being joined. Common columns are columns that have the same name in both tables. A NATURAL JOIN can be an INNER join, a LEFT OUTER join, or a RIGHT The default is INNER join A. Left outer join B. Right outer join C. Full outer join D. None of the above. View Answer . 4. Relation R1 has 10 tuples and 5 attributes. Relation R2 has 0 tuples and 7 attributes. When a CROSS JOIN is achieved between R1 and R2, how many tuples would the resultant set have? A. 28 B. 10 C. 0 D. 35. View Answer. 5. Which join is to be used between two tables A and B when the resultant table. Moreover, there are several types of Hive join - HiveQL Select Joins: Hive inner join, hive left outer join, hive right outer join, and hive full outer join. We will also learn Hive Join tables in depth. Hive Join - HiveQL Select Joins Query. 2. Apache Hive Join - HiveQL Select Joins Query . Basically, for combining specific fields from two tables by using values common to each one we.
Inner join and left outer join are only different where one of the involved tables does not contain any suitable record that meets the join conditions. With an inner join (table1 inner join table2), no record is included in the results set in this case. However, this means that the corresponding record from table 1 is not considered in the results set. In this case, with a left outer join. LEFT INNER JOIN vs. LEFT OUTER JOIN-OUTERに時間がかかるのはなぜですか？ 以下のクエリがあります。 LEFT OUTER結合の使用は、実行に9秒かかります。 LEFT OUTERをLEFT INNERに変更すると、実行時間が2秒に短縮され、same行数が返されます。 dbo.Acceptsテーブルの同じ数の行が処理されているので、結合の種類に. Una combinación interna (JOIN o INNER JOIN, CROSS JOIN o coma) primero hace una CROSS JOIN. (Es decir, devuelve todas las filas que se pueden hacer agregando una fila desde su tabla izquierda y una fila desde su tabla derecha.) Luego, cualquier ON elimina las filas que no cumplen con su condición. Un OUTER JOIN devuelve las filas de un INNER JOIN [Spark报错]:Detected cartesian product for LEFT OUTER join between logical plansFBI warning：xian si kao yao bu yao di ka er cha xun, If true Then return注意：先思考一下自己sql语句是不是真的需要笛卡尔查询，如果是的话，本文跳过开门见山测试程序..