You want to declare two integer variables x and y, assign 15 to x and 30 to y, then swap their values inside a PL/pgSQL block. Which code snippet correctly performs this swap?
hard📝 Application Q8 of 15
PostgreSQL - PL/pgSQL Fundamentals
You want to declare two integer variables x and y, assign 15 to x and 30 to y, then swap their values inside a PL/pgSQL block. Which code snippet correctly performs this swap?
ADECLARE
x integer := 15;
y integer := 30;
temp integer;
BEGIN
temp := x;
x := y;
y := temp;
END;
BDECLARE
x integer := 15;
y integer := 30;
BEGIN
x := y;
y := x;
END;
CDECLARE
x integer := 15;
y integer := 30;
BEGIN
x = y;
y = x;
END;
DDECLARE
x integer := 15;
y integer := 30;
BEGIN
x := x + y;
y := x - y;
x := x - y;
END;
Step-by-Step Solution
Solution:
Step 1: Understand the Swap Logic
Swapping two variables requires a temporary variable to hold one value during the exchange.
Step 2: Analyze Options
DECLARE
x integer := 15;
y integer := 30;
temp integer;
BEGIN
temp := x;
x := y;
y := temp;
END; uses a temporary variable temp to hold x's value, then assigns y to x, and finally assigns temp to y, correctly swapping the values.
Step 3: Identify Incorrect Options
DECLARE
x integer := 15;
y integer := 30;
BEGIN
x := y;
y := x;
END; overwrites x with y and then assigns x (already overwritten) to y, losing original x value. DECLARE
x integer := 15;
y integer := 30;
BEGIN
x = y;
y = x;
END; uses '=' instead of ':=' for assignment, which is invalid. DECLARE
x integer := 15;
y integer := 30;
BEGIN
x := x + y;
y := x - y;
x := x - y;
END; uses arithmetic swap logic but is missing the declaration of temp and is more complex than necessary.
Final Answer:
DECLARE
x integer := 15;
y integer := 30;
temp integer;
BEGIN
temp := x;
x := y;
y := temp;
END; correctly swaps the values using a temporary variable.
Quick Check:
Use temp variable for swap [OK]
Quick Trick:Use a temp variable to swap values [OK]
Common Mistakes:
Overwriting variables without temp storage
Using '=' instead of ':=' for assignment
Not declaring temporary variable
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