Which statements will be able to show the following result set?
a
.
)
SELECT invoice
_
id
,
total, last
_
name
FROM invoice
JOIN customer
USING
(
invoice
.
customer
_
id
=
customer.customer
_
id
)
;
b
.
)
SELECT invoice
_
id
,
total, last
_
name
FROM invoice, customer;
c
.
)
SELECT invoice
_
id
,
total, last
_
name
FROM invoice
JOIN customer
USING
(
customer
_
id
)
;
d
.
)
SELECT invoice
_
id
,
total, last
_
name
FROM invoice
WHERE customer
_
id
!
=
NULL;
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Question

Which statements will be able to show the following result set?
a
.
)
SELECT invoice
_
id
,
 ﻿total, last
_
name
FROM invoice
JOIN customer
USING 
(
invoice
.
customer
_
id 
=
 ﻿customer.customer
_
id
)
;
b
.
)
SELECT invoice
_
id
,
 ﻿total, last
_
name
FROM invoice, customer;
c
.
)
SELECT invoice
_
id
,
 ﻿total, last
_
name
FROM invoice
JOIN customer
USING 
(
customer
_
id
)
;
d
.
)
SELECT invoice
_
id
,
 ﻿total, last
_
name
FROM invoice
WHERE customer
_
id 
!
=
 ﻿NULL;
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Accepted Answer

⚹ To determine which SQL statement will produce the desired result set, we need to analyze each option given the requirement to join the "invoice" and "customer" tables and select the columns "invoice_id", "total", and "last_name". ⚹ ⚹ Option a) attempts to use the `USING` clause but the syntax is incorrect because `USING` should be followed by a list of column names in parentheses without the table names or the equality operator. ⚹ ⚹ Option b) uses the old-style comma-separated join, which results in a Cartesian product of the two tables. This is not a proper join and will not filter the rows based on related columns. ⚹ ⚹ Option c) correctly uses the `USING` clause with the proper syntax, specifying the common column "customer_id" that exists in both tables. This will result in a proper join where the "invoice" and "customer" tables are matched on the "customer_id" column. ⚹ ⚹ Option d) is not a join operation at all. It is a simple `SELECT` from the "invoice" table with a `WHERE` clause that filters out rows where "customer_id" is not NULL, which does not involve the "customer" table. ⚹ ⚹ The correct statement that will show the desired result set is option c). ⚹

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