slide môn học MySQL bài 5 using joins

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Using Joins Session 10 Review  Primary key is a unique identifier in a table Foreign key is a primary key in a different table    The DISTINCT option in the SELECT command enables user to view the distinct values for a column Grouping facilitates to group rows with similar values for a specific column into a single row in order to operate on them together Keys are pieces of information that helps to identify a record in a table MySQL Database / Session 10 / Slide of 22 Objectives       Concept of Joining Tables Equi-Join Inner-Join Outer-Join Self-Join Sub-Selects and UNION MySQL Database / Session 10 / Slide of 22 Concept of Joining Tables  Combining two or more records of different tables from the same database, into one complete structure, is known as joining of tables  The tables can be joined either by using WHERE clause with SELECT command or by using JOIN keyword with SELECT command MySQL Database / Session 10 / Slide of 22 Equi Join-I  An Equi-Join displays only those records where a match is found in both the tables The syntax for Equi-Join is: SELECT column_name, [*] FROM table1 [as alias],table2 [as alias] WHERE (join_condition); MySQL Database / Session 10 / Slide of 22 Equi Join-II  Display first name, department name and designation of all employees from EMP_DETAILS and EMP_DEPARTMENT tables SELECT EMP_DETAILS.E_FNAME,EMP_DEPARTMENT D_NAME,EMP_DEPARTMENT.DESIGNATION FROM EMP_DETAILS,EMP_DEPARTMENT WHERE (EMP_DETAILS.E_ID = EMP_DEPARTMENT.E_ID); MySQL Database / Session 10 / Slide of 22 Inner Join-I  An INNER JOIN creates a virtual table by combining the fields of both tables that satisfy the query for both the tables The syntax for inner-join is: SELECT column_name1, column_name2, column_name3 FROM table_name1 INNER JOIN table_name2 ON table_name1.primary_keyfield = table_name2.foreign_keyfield; MySQL Database / Session 10 / Slide of 22 Inner Join-II  Display first name, department name, and designation of all employees from EMP_DETAILS and EMP_DEPARTMENT tables SELECT EMP_DETAILS.E_FNAME,EMP_DEPARTMENT D_NAME,EMP_DEPARTMENT.DESIGNATION FROM EMP_DETAILS INNER JOIN EMP_DEPARTMENT ON EMP_DETAILS.E_ID = EMP_DEPARTMENT.E_ID; MySQL Database / Session 10 / Slide of 22 Inner Join-III  Display all the employees whose E_ID are same and who live in California city SELECT EMP_DETAILS.E_FNAME,EMP_DEPARTMENT.D_NAME, EMP_DETAILS.E_ADDRESS FROM EMP_DETAILS INNER JOIN EMP_DEPARTMENT ON (EMP_DETAILS.E_ID = EMP_DEPARTMENT.E_ID) AND (EMP_DETAILS.E_ADDRESS = ‘CALIFORNIA’); MySQL Database / Session 10 / Slide of 22 Inner Join using table aliases  Display employee details using table aliases SELECT E.E_FNAME, E.E_LNAME S.BASIC_SALARY FROM EMP_DETAILS AS E, EMP_SALARY AS S WHERE E.E_ID = S.E_ID; MySQL Database / Session 10 / Slide 10 of 22 Outer Join  An OUTER JOIN displays even those rows of the tables that may not have any matching value in the other tables to appear in the result set There are three types of outer join They are:  Left Outer Join Right Outer Join Full Outer Join   MySQL Database / Session 10 / Slide 11 of 22 Left Outer Join-I  Left Outer Join: Displays all rows from the table specified on the left of the OUTER JOIN operator in the result set, with or without any match with the table specified on the right The syntax is: SELECT COLUMN1, COLUMN2 FROM TABLE1 LEFT OUTER JOIN TABLE2 ON (JOIN_ CONDITION); MySQL Database / Session 10 / Slide 12 of 22 Left Outer Join-II  Display all the records from EMP_DETAILS, EMP_SALARY, and EMP_DEPARTMENT tables by joining them with the common attribute E_ID SELECT E_FNAME,E_LNAME,E_ADDRESS FROM EMP_DETAILS LEFT JOIN EMP_SALARY ON EMP_DETAILS.E_ID = EMP_SALARY.E_ID LEFT JOIN EMP_DEPARTMENT ON EMP_SALARY.E_ID = EMP_DEPARTMENT.E_ID; MySQL Database / Session 10 / Slide 13 of 22 Right Outer Join-I  Right Outer Join: Displays all rows from the table specified on the right of the OUTER JOIN operator in the result set, with or without any match with the table specified on the left The syntax is: SELECT COLUMN1, COLUMN2 FROM TABLE1 RIGHT OUTER JOIN TABLE2 ON (JOIN_ CONDITION); MySQL Database / Session 10 / Slide 14 of 22 Right Outer Join-II  Display records of E_LNAME, E_ADDRESS and E_PHONE_NO from EMP_DETAILS table where the employee ids are greater than 102 SELECT DISTINCT E_LNAME,E_ADDRESS,E_PHONE_ NO FROM EMP_DETAILS E RIGHT OUTER JOIN EMP_DEPARTMENT D ON(E.E_ID > 102); MySQL Database / Session 10 / Slide 15 of 22 Self-Join-I  A Self-Join is a query that is used to join or compare a table to itself The syntax is: SELECT DISTINCT COLUMN1,COLUMN2 FROM TABLE WHERE (JOIN_CONDITION); MySQL Database / Session 10 / Slide 16 of 22 Self-Join-II  Display all the employees, who are located in the same city SELECT DISTINCT E1.E_ID, E1.E_FNAME,E1.E_LNAME, E.E_ADDRESS FROM EMP_DETAILS AS E1,EMP_DETAILS AS E2 WHERE E1.E_ADDRESS = E2.E_ADDRESS AND E1.E_ADDRESS IS NOT NULL AND E2.E_ADDRESS IS NOT NULL AND E1.E_ID E2.E_ID ORDER BY E1.E_ADDRESS,E1.E_ID; MySQL Database / Session 10 / Slide 17 of 22 Sub-Select-I  Sub-Select: When a SELECT query is placed inside another SELECT query, then the inner SELECT query is said to be Sub-Select query The syntax is: SELECT [*] column_name… FROM table_name1 WHERE column_name IN (SELECT column_name FROM table_name2); MySQL Database / Session 10 / Slide 18 of 22 Sub-Select-II  Display all records from EMP_DETAILS and EMP_DEPARTMENT tables using sub-selects SELECT * FROM EMP_DETAILS WHERE E_ID IN (SELECT E_ID FROM EMP_DEPARTMENT); MySQL Database / Session 10 / Slide 19 of 22 UNION-I  Union is used to combine many result sets used with SELECT command into a single result set The syntax is: SELECT * FROM TABLE1 UNION [ALL | DISTINCT] SELECT * FROM TABLE2 UNION [ALL | DISTINCT] MySQL Database / Session 10 / Slide 20 of 22 UNION-II  Display all the records from EMP_DETAILS table where the employee addresses are California and Troy (SELECT * FROM EMP_DETAILS WHERE E_ADDRESS = ‘TROY’ORDER BY E_ID LIMIT 2)UNION (SELECT * FROM EMP_DETAILS WHERE E_ADDRESS =‘CALIFORNIA’ ORDER BY E_ID LIMIT 1) ORDER BY E_ID; MySQL Database / Session 10 / Slide 21 of 22 Summary       Joining of tables means combining two or more records of different tables of the same database into one comprehensive structure The tables can be joined either with the WHERE clause used with SELECT command or by using the JOIN keyword In an Equi-Join, the comparison is made between two columns that carry same values An INNER JOIN creates a virtual table by combining the fields of both tables that satisfy the query for both the tables Union is used to combine many result sets used with SELECT command into a single result set A select query used inside another select query is known as Sub-selects query MySQL Database / Session 10 / Slide 22 of 22 [...]... E_LNAME,E_ADDRESS,E_PHONE_ NO FROM EMP_DETAILS E RIGHT OUTER JOIN EMP_DEPARTMENT D ON(E.E_ID > 102); MySQL Database / Session 10 / Slide 15 of 22 Self-Join-I  A Self-Join is a query that is used to join or compare a table to itself The syntax is: SELECT DISTINCT COLUMN1,COLUMN2 FROM TABLE WHERE (JOIN_CONDITION); MySQL Database / Session 10 / Slide 16 of 22 Self-Join-II  Display all the employees, who are located in the... EMP_DEPARTMENT tables using sub-selects SELECT * FROM EMP_DETAILS WHERE E_ID IN (SELECT E_ID FROM EMP_DEPARTMENT); MySQL Database / Session 10 / Slide 19 of 22 UNION-I  Union is used to combine many result sets used with SELECT command into a single result set The syntax is: SELECT * FROM TABLE1 UNION [ALL | DISTINCT] SELECT * FROM TABLE2 UNION [ALL | DISTINCT] MySQL Database / Session 10 / Slide 20 of 22... Outer Join   MySQL Database / Session 10 / Slide 11 of 22 Left Outer Join-I  Left Outer Join: Displays all rows from the table specified on the left of the OUTER JOIN operator in the result set, with or without any match with the table specified on the right The syntax is: SELECT COLUMN1, COLUMN2 FROM TABLE1 LEFT OUTER JOIN TABLE2 ON (JOIN_ CONDITION); MySQL Database / Session 10 / Slide 12 of 22... E2.E_ID ORDER BY E1.E_ADDRESS,E1.E_ID; MySQL Database / Session 10 / Slide 17 of 22 Sub-Select-I  Sub-Select: When a SELECT query is placed inside another SELECT query, then the inner SELECT query is said to be Sub-Select query The syntax is: SELECT [*] column_name… FROM table_name1 WHERE column_name IN (SELECT column_name FROM table_name2); MySQL Database / Session 10 / Slide 18 of 22 Sub-Select-II  Display... EMP_DEPARTMENT.E_ID; MySQL Database / Session 10 / Slide 13 of 22 Right Outer Join-I  Right Outer Join: Displays all rows from the table specified on the right of the OUTER JOIN operator in the result set, with or without any match with the table specified on the left The syntax is: SELECT COLUMN1, COLUMN2 FROM TABLE1 RIGHT OUTER JOIN TABLE2 ON (JOIN_ CONDITION); MySQL Database / Session 10 / Slide 14 of 22... E_ADDRESS =‘CALIFORNIA’ ORDER BY E_ID LIMIT 1) ORDER BY E_ID; MySQL Database / Session 10 / Slide 21 of 22 Summary       Joining of tables means combining two or more records of different tables of the same database into one comprehensive structure The tables can be joined either with the WHERE clause used with SELECT command or by using the JOIN keyword In an Equi-Join, the comparison is made... both the tables Union is used to combine many result sets used with SELECT command into a single result set A select query used inside another select query is known as Sub-selects query MySQL Database / Session 10 / Slide 22 of 22
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