有关SQLite的substr函数的笔记

官方参考文档：SQLite Query Language: Core Functions

测试SQL语句：

SELECT substr(2012-12-12 10:11:12 fff,0,20) AS substr_0_20,
substr(2012-12-12 10:11:12 fff,0,19) AS substr_0_19,
substr(2012-12-12 10:11:12 fff,1,19) AS substr_1_19,
substr(2012-12-12 10:11:12 fff,19) AS substr_19

SELECT substr(2012-12-12 10:11:12 fff,0,20) AS substr_0_20, substr(2012-12-12 10:11:12 fff,0,19) AS substr_0_19, substr(2012-12-12 10:11:12 fff,1,19) AS substr_1_19, substr(2012-12-12 10:11:12 fff,19) AS substr_19

WINDOW上的Navicat、Mac上的MesaSQLite、Android上SQLite上测试语句结果：substr_0_20 和 substr_1_19结果保持一致；substr_0_19不知道为啥会少一位？

substr_0_20 substr_0_19 substr_1_19 substr_19 2012-12-12 10:11:12 2012-12-12 10:11:1 2012-12-12 10:11:12 2 fff

IOS的FMDB上测试结果：substr_0_20不知道为啥会多一位？

substr_0_20 substr_0_19 substr_1_19 substr_19 2012-12-12 10:11:12 2012-12-12 10:11:12 2012-12-12 10:11:12 2 fff

到底哪个是正常的呢？

官方参考文档：SQLite Query Language: Core Functions 测试SQL语句： SELECT substr(2012-12-12 10:11:12 fff,0,20) AS substr_0_20, substr(2012-12-12 10:11:12 fff,0,19) AS substr_0_19, substr(2012-12-12 10:11:12 fff,1,19) AS substr_1_19, substr(2012-12-12 10:11:12 fff,19) AS substr_19 WINDOW上的Navicat、Mac上的MesaSQLite、Android上SQLite上测试语句结果：substr_0_20 和 substr_1_19结果保持一致；substr_0_19不知道为啥会少一位？ substr_0_20 substr_0_19 substr_1_19 substr_19 2012-12-12 10:11:12 2012-12-12 10:11:1 2012-12-12 10:11:12 2 fff IOS的FMDB上测试结果：substr_0_20不知道为啥会多一位？ substr_0_20 substr_0_19 substr_1_19 substr_19 2012-12-12 10:11:12 2012-12-12 10:11:12 2012-12-12 10:11:12 2 fff 到底哪个是正常的呢？