1. Table Joins
Part II

2. Joining Tables
Used to query data from 2 or more tables using 1 SELECT statement.
The 2 tables must have at least one common column
Columns do not have to have the same name

3. Oracle vs ANSI Standard
SELECT spriden_id CSU_ID
,spriden_last_name Stdt_Name
FROM spriden
,spraddr
WHERE spriden_pidm = spraddr_pidm
AND spraddr_atyp_code = 'MA'
AND spraddr_zip like '80523%'
AND spriden_change_ind IS NULL
ORDER BY Stdt_Name
ANSI Standard
SELECT spriden_id CSU_ID
,spriden_last_name Stdt_Name
FROM spriden
JOIN spraddr
ON spraddr_pidm = spriden_pidm
WHERE spraddr_atyp_code = 'MA'
AND spraddr_zip like '80523%'
AND spriden_change_ind IS NULL
ORDER BY Stdt_Name

4. Column Ambiguously Defined
If the column names in the two tables are the same, dot notation must be used
table_name.column_name
SELECT csus_term_info_fal.csu_id CSU_ID
,csus_term_info_fal.name Stdt_Name
,trn_amount Tuition
FROM csus_term_info_fal
JOIN csut_ar_trn
ON csus_term_info_fal.pidm = csut_ar_trn.pidm
WHERE csut_ar_trn.term_code = ‘200790’
AND category_code = ‘TUI’

5. Column Ambiguously Defined
table_alias.column_name
SELECT ti.csu_id CSU_ID
,ti.name Stdt_Name
,ar.trn_amount Tuition
FROM csus_term_info_fal ti
JOIN csut_ar_trn ar
ON ti.pidm = ar.pidm
WHERE ar.term_code = ‘200790’
AND ar.category_code = ‘TUI’
Error will result if Oracle cannot determine which column to use

6. Different Types of Joins
Inner Join
Most common
Data in the joining columns must match for results to be returned
Outer Join
Returns all rows from the “outer” table and only the rows with matching data in the joining columns from the other table(s)
Self Join
Data from one column of a table is related to the data in another column of the same table
Create alias’ for the table and use an inner or outer join
Cartesian Product
Every row of the 1st table is returned with every row of the 2nd table
Usually a mistake

7. Example Inner Join
How many students have registered for at least one on-campus class?

8. Example Inner Join
How many students have registered for at least one on-campus class?
SELECT sfrstcr_term_code Term
,COUNT(DISTINCT sfrstcr_pidm) Count
FROM sfrstcr
INNER JOIN stvrsts
ON stvrsts_code = sfrstcr_rsts_code
JOIN ssbsect
ON ssbsect_term_code = sfrstcr_term_code
AND ssbsect_crn = sfrstcr_crn
WHERE stvrsts_incl_sect_enrl = 'Y'
AND ssbsect_camp_code = 'M'
GROUP BY sfrstcr_term_code
ORDER BY Term

9. Example Inner Join
Results

10. Example Outer Join
For how many credits has every person in the database registered?

11. Example Outer Join
For how many credits has every person in the database registered?
SELECT i.spriden_id CSU_ID
,i.spriden_last_name || ', ' || i.spriden_first_name Stdt_Name
,SUM(NVL(c.sfrstcr_credit_hr, 0)) Credit_Hrs
FROM spriden i
LEFT OUTER JOIN
sfrstcr c
ON c.sfrstcr_pidm = i.spriden_pidm
WHERE i.spriden_change_ind IS NULL
GROUP BY i.spriden_id
,i.spriden_last_name || ', ' || i.spriden_first_name
ORDER BY Credit_Hrs
,Stdt_Name

12. Example Outer Join
Results

13. Example Self Join
Identify the students who have registered for Continuous Registration in addition to another course.

14. Example Self Join
Identify the students who have registered for Continuous Registration in addition to another course.
SELECT DISTINCT
i.spriden_id
,i.spriden_last_name
,i.spriden_first_name
,r.sfrstcr_term_code
FROM sfrstcr r
JOIN sfrstcr rx
ON rx.sfrstcr_pidm = r.sfrstcr_pidm
AND rx.sfrstcr_term_code = r.sfrstcr_term_code
JOIN spriden i
ON i.spriden_pidm = r.sfrstcr_pidm
JOIN ssbsect s
ON s.ssbsect_term_code = r.sfrstcr_term_code
AND s.ssbsect_crn = rx.sfrstcr_crn
WHERE i.spriden_change_ind IS NULL
AND s.ssbsect_subj_code = 'CR'
AND s.ssbsect_crse_numb = 'CONRG’
AND r.sfrstcr_crn <> s.ssbsect_crn
AND r.sfrstcr_rsts_code NOT IN ('CW', 'XF', 'XE', 'XD')
ORDER BY r.sfrstcr_term_code

15. Example Self Join
Identify the students who have registered for Continuous Registration in addition to another course.

16. Example Cartesian Product
How many active mailing addresses have a zip code of 80523?

17. Example Cartesian Product
How many active mailing addresses have a zip code of 80523?
SELECT COUNT(*)
FROM spriden
,spraddr
WHERE spraddr_atyp_code = 'MA'
AND SYSDATE BETWEEN NVL(spraddr_from_date, (to_date('01-JAN-1900', 'DD-MON-YYYY')))
AND NVL(spraddr_to_date, (to_date('31-DEC-2099', 'DD-MON-YYYY')))
AND spraddr_zip LIKE '80523%'
AND spriden_change_ind IS NULL
8 minutes later… 1,367,196,180
What’s wrong? The answer should be 3,212

18. Questions?