SQLiteselect哪里空？

在SQLite中，如何selectsome_column为空的logging？
空作为NULL和“”计数。

Answer 1

有几种方法，如：

where some_column is null or some_column = '' 

要么

 where ifnull(some_column, '') = '' 

要么

 where coalesce(some_column, '') = '' 

的

 where ifnull(length(some_column), 0) = 0 

Answer 2

看起来你可以简单地做：

 SELECT * FROM your_table WHERE some_column IS NULL OR some_column = ''; 

testing用例：

 CREATE TABLE your_table (id int, some_column varchar(10)); INSERT INTO your_table VALUES (1, NULL); INSERT INTO your_table VALUES (2, ''); INSERT INTO your_table VALUES (3, 'test'); INSERT INTO your_table VALUES (4, 'another test'); INSERT INTO your_table VALUES (5, NULL); 

结果：

 SELECT id FROM your_table WHERE some_column IS NULL OR some_column = ''; id ---------- 1 2 5 

Answer 3

也许你的意思是

 select x from some_table where some_column is null or some_column = '' 

但是由于你没有真正提出问题，所以我不能说。

Answer 4

你可以用以下方法做到这一点：

 int counter = 0; String sql = "SELECT projectName,Owner " + "FROM Project WHERE Owner= ?"; PreparedStatement prep = conn.prepareStatement(sql); prep.setString(1, ""); ResultSet rs = prep.executeQuery(); while (rs.next()) { counter++; } System.out.println(counter); 

这会给你列值为空或空白的行号。