sqlite的模式匹配不起作用的原因是什么？

Question

我有一个包含日志数据的数据库文件。该数据库包含一个表LOG，该表包含一个列MSG。表中有30行，其中MSG列在行尾包含字符串“ down”：

$ sqlite3 log.db "select msg from log" | grep down$ | wc -l
30

但是当我尝试用LIKE查找它们时，没有找到匹配项：

$ sqlite3 log.db "select msg from log where msg like '%down'" | grep down$ | wc -l
0

这可能是什么原因？

更新：MCVE

CREATE TABLE LOG (MSG VARCHAR(6291456) NOT NULL);

INSERT INTO LOG VALUES (X'666163696c6974793d6461656d6f6e3b636f6d706f6e656e743d6e616d65643b746578743d7368757474696e6720646f776e');

SELECT MSG FROM LOG;                                         -- returns the row
SELECT MSG FROM LOG WHERE MSG LIKE '%down';                  -- returns nothing
SELECT MSG FROM LOG WHERE MSG LIKE '%down%';                 -- returns nothing
SELECT MSG FROM LOG WHERE CAST(MSG AS VARCHAR) LIKE '%down'; -- returns the row

我不知道为什么从VARCHAR到VARCHAR的转换会有所不同。

更新：另一个MCVE

CREATE TABLE LOG (MSG VARCHAR(6291456) NOT NULL);

INSERT INTO LOG VALUES (X'666163696c6974793d6461656d6f6e3b636f6d706f6e656e743d6e616d65643b746578743d7368757474696e6720646f776e');
INSERT INTO LOG VALUES ('facility=daemon;component=named;text=shutting down');

SELECT ROWID,MSG FROM LOG;                                         -- returns both rows

SELECT ROWID,MSG FROM LOG WHERE MSG LIKE '%down';                  -- returns just the second

SELECT ROWID,MSG FROM LOG WHERE MSG LIKE '%down%';                 -- returns just the second

SELECT ROWID,MSG FROM LOG WHERE CAST(MSG AS VARCHAR) LIKE '%down'; -- returns both the row

SELECT HEX(MSG) FROM LOG;

Answer 1

我会将其粘贴到注释中，但是格式看起来很难看。它对我有用：

$ sqlite3 log.db
SQLite version 3.24.0 2018-06-04 14:10:15
Enter ".help" for usage hints.
sqlite> create table log (id int, msg text);
sqlite> insert into log values (1,'database is down');
sqlite> insert into log values (2,'database is down');
sqlite> insert into log values (3,'database is down');
sqlite> ^D
$ sqlite3 log.db "select msg from log" | grep down$ | wc -l
       3
$ sqlite3 log.db "select msg from log where msg like '%down'" | grep down$ | wc -l
       3

您可以共享log表的内容，所以我可以尝试重现您的问题吗？