PL/SQL daily question: difference between a CASE statement and a CASE expression

PL/SQL daily question: the difference between a CASE statement and a CASE expression: there are many different types of guinea pigs in the world, some of which have identifiable characteristics. For example, the "Abyssinians" skin has a pleated garlands www.2cto.com "Texels" with long curly hair. In contrast, the White Crested Guinea Pig on the header contains a White pattern (as expected). Each of the following options provides an implementation method for the plch_proc process, it displays the guinea pigs with the given features. This process is incomplete. Which of the following lines will be displayed after the following code blocks are executed? [SQL] www.2cto.com Species = Texel Species = BEGIN plch_proc ('curly '); plch_proc ('white'); END;/[SQL] () create or replace procedure plch_proc (feature_in VARCHAR2) IS invalid VARCHAR2 (100); begin case feature_in WHEN 'curly 'then usage: = 'text'; WHEN 'rosettes 'THEN usage: = 'abyssinian '; end case; DBMS_OUTPUT.put_line ('species =' | l_guinea_pig_species); END;/(B) CREATE OR REPLACE PROCEDURE plch_proc (feature_in VARCHAR2) IS l_guinea_pig_species VARCHAR2 (100); BEGIN l_guinea_pig_species: = CASE feature_in WHEN 'curly 'then' Texel 'when' rosettes 'then' Abyssinian 'end; sums ('species = '| l_guinea_pig_species); END;/(C) create or replace procedure plch_proc (feature_in IN VARCHAR2) IS l_guinea_pig_species VARCHAR2 (100 ); begin case feature_in WHEN 'curly 'THEN l_guinea_pig_species: = 'text'; WHEN 'rosettes' THEN l_guinea_pig_species: = 'abyssinian '; else null; end case; sums ('species = '| l_guinea_pig_species); END;/(D) create or replace procedure plch_proc (feature_in IN VARCHAR2) IS l_guinea_pig_species VARCHAR2 (100 ); begin if feature_in = 'curly 'then l_guinea_pig_species: = 'text'; ELSIF feature_in = 'rosettes 'then l_guinea_pig_species: = 'abyssinian '; end if; DBMS_OUTPUT.put_line ('species = '| l_guinea_pig_species); END;/answer: -- BCD pay attention to the CASE statement (statement) and CASE expression (expression) the difference in the absence of else a is a case statement, encounter A branch without processing and the lack of ELSE clause will report an error: "ORA-06592: CASE not found while executing CASE statement "B uses a CASE expression and returns NULL C: With ELSE NULL protection D: IF statements do not report errors because they do not meet the conditions.