mysql LEFT JOIN keyword


  Translation results：

left

UK[left] 美[lɛft]

adj.Left, left;leftist

n.Left , left; [military] left wing; left wing, radical

adv. to the left; on the left

v. to leave (past tense and past participle of leave)

plural ： lefts

join

UK[dʒɔɪn] US[dʒɔɪn]

vt.& vi.Join;participate;connect;connection

vt.Participate; combine; get on (train, plane, etc.); get on (road)

n.Connect; combine; join; joint point

Third person singular: joins now Participle: joining Past tense: joined Past participle: joined

mysql LEFT JOIN keywordsyntax

Function:The LEFT JOIN keyword will return all rows from the left table (table_name1), even if there are no matching rows in the right table (table_name2).

Syntax: SELECT column_name(s) FROM table_name1 LEFT JOIN table_name2 ON table_name1.column_name=table_name2.column_name

Comments: In some databases , LEFT JOIN is called LEFT OUTER JOIN.

mysql LEFT JOIN keywordexample

//列出所有的人，以及他们的定购 - 如果有的话
SELECT Persons.LastName, Persons.FirstName, Orders.OrderNo FROM Persons LEFT JOIN Orders ON Persons.Id_P=Orders.Id_P ORDER BY Persons.LastName;

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