How can you efficiently retrieve data from multiple interconnected tables using inner joins in Access SQL?

Access-SQL: Achieving Inner Joins with Multiple Tables

When working with relational databases, efficiently retrieving data from multiple interconnected tables is crucial. In Access, the inner join operation allows you to combine data from these tables based on a shared field.

Suppose we have five tables: tblOjt, tblStudent, tblCourse, tblCompany, and tblAddressee. Our goal is to extract specific information from these tables, including:

• ID from tblOjt
• Last name, first name, and middle name from tblStudent
• Course from tblCourse
• Company name from tblCompany
• Addressee name from tblAddressee
• Date added from tblOjt
• Date started from tblOjt
• Date ended from tblOjt
• OJT hours from tblOjt

Syntax for Multiple Inner Joins in Access

In Access SQL, to perform inner joins on multiple tables, the following syntax is required:

SELECT
  t1.c1,
  t2.c2,
  ...
  tN.cN
FROM (
  (
    t1
    INNER JOIN t2 ON t1.something = t2.something
  )
  INNER JOIN t3 ON t2.something = t3.something
)
INNER JOIN...

• t1-tN represent the tables being joined.
• c1-cN are the columns you want to retrieve.
• Parentheses enclose successive pairs of tables to be joined.

Applying the Syntax to Our Example

Using this syntax, we can construct the following SQL statement to retrieve the desired data:

SELECT
  tblOjt.ID AS ojtid,
  tblStudent.lastname,
  tblStudent.firstname,
  tblStudent.middlename,
  tblCourse.coursealias AS course,
  tblCompany.companyname,
  tblAddressee.addresseename,
  tblOjt.dateadded AS dateadded,
  tblOjt.datestarted AS datestarted,
  tblOjt.dateended AS dateended,
  tblOjt.ojthours AS ojthours
FROM (
  (
    tblOjt
    INNER JOIN tblStudent ON tblOjt.studentid = tblStudent.ID
  )
  INNER JOIN tblCourse ON tblStudent.course = tblCourse.ID
)
INNER JOIN tblCompany ON tblOjt.companyid = tblCompany.ID
INNER JOIN tblAddressee ON tblOjt.addresseeid = tblAddressee.ID

Conclusion

By understanding the syntax for performing inner joins on multiple tables in Access-SQL, you can effectively retrieve data from complex database structures. The example provided demonstrates how to apply this knowledge to extract specific information from multiple interconnected tables.

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