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这篇文章主要介绍“数据库 CLOB 为空的判断方法是什么”，在日常操作中，相信很多人在数据库 CLOB 为空的判断方法是什么问题上存在疑惑，丸趣 TV 小编查阅了各式资料，整理出简单好用的操作方法，希望对大家解答”数据库 CLOB 为空的判断方法是什么”的疑惑有所帮助！接下来，请跟着丸趣 TV 小编一起来学习吧！
下列的哪些选项在执行之后会显示 CLOB has a length of 0 ?
(A)
DECLARE
l_clob CLOB;
BEGIN
IF l_clob IS NULL
THEN
DBMS_OUTPUT.put_line ( CLOB is NULL
ELSE
DBMS_OUTPUT.put_line ( CLOB has a length of
|| LENGTH (l_clob));
END IF;
/SQL DECLARE
2 l_clob CLOB;
3 BEGIN
4 IF l_clob IS NULL
5 THEN
6 DBMS_OUTPUT.put_line ( CLOB is NULL
7 ELSE
8 DBMS_OUTPUT.put_line ( CLOB has a length of
9 || LENGTH (l_clob));
10 END IF;
11 END;
12 /
CLOB is NULL
PL/SQL procedure successfully completed
SQL(B)
DECLARE
l_clob CLOB := EMPTY_CLOB ();
BEGIN
IF l_clob IS NULL
THEN
DBMS_OUTPUT.put_line ( CLOB is NULL
ELSE
DBMS_OUTPUT.put_line ( CLOB has a length of
|| LENGTH (l_clob));
END IF;
/SQL DECLARE
2 l_clob CLOB := EMPTY_CLOB ();
3 BEGIN
4 IF l_clob IS NULL
5 THEN
6 DBMS_OUTPUT.put_line ( CLOB is NULL
7 ELSE
8 DBMS_OUTPUT.put_line ( CLOB has a length of
9 || LENGTH (l_clob));
10 END IF;
11 END;
12 /
CLOB has a length of 0
PL/SQL procedure successfully completed
SQL(C)
DECLARE
l_clob CLOB :=
BEGIN
IF l_clob IS NULL
THEN
DBMS_OUTPUT.put_line ( CLOB is NULL
ELSE
DBMS_OUTPUT.put_line ( CLOB has a length of
|| LENGTH (l_clob));
END IF;
/SQL DECLARE
2 l_clob CLOB :=
3 BEGIN
4 IF l_clob IS NULL
5 THEN
6 DBMS_OUTPUT.put_line ( CLOB is NULL
7 ELSE
8 DBMS_OUTPUT.put_line ( CLOB has a length of
9 || LENGTH (l_clob));
10 END IF;
11 END;
12 /
CLOB is NULL
PL/SQL procedure successfully completed
SQL(D)
DECLARE
l_clob1 CLOB := EMPTY_CLOB ();
l_clob2 CLOB := l_clob1;
BEGIN
IF l_clob2 IS NULL
THEN
DBMS_OUTPUT.put_line ( CLOB is NULL
ELSE
DBMS_OUTPUT.put_line ( CLOB has a length of
|| LENGTH (l_clob2));
END IF;
/SQL DECLARE
2 l_clob1 CLOB := EMPTY_CLOB ();
3 l_clob2 CLOB := l_clob1;
4 BEGIN
5 IF l_clob2 IS NULL
6 THEN
7 DBMS_OUTPUT.put_line ( CLOB is NULL
8 ELSE
9 DBMS_OUTPUT.put_line ( CLOB has a length of
10 || LENGTH (l_clob2));
11 END IF;
12 END;
13 /
CLOB has a length of 0
PL/SQL procedure successfully completed答案 BD. 注意答案 C 里面的 相当于 NULL.
到此，关于“数据库 CLOB 为空的判断方法是什么”的学习就结束了，希望能够解决大家的疑惑。理论与实践的搭配能更好的帮助大家学习，快去试试吧！若想继续学习更多相关知识，请继续关注丸趣 TV 网站，丸趣 TV 小编会继续努力为大家带来更多实用的文章！
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