Notes on the SUBSTR function of SQLite

Official Reference Document: SQLite Query language:core Functions http://www.sqlite.org/lang_corefunc.html

To test the SQL statement:

SELECTSubstr'2012-12-12 10:11:12 FFF',0, -) asSubstr_0_20,substr ('2012-12-12 10:11:12 FFF',0, +) asSubstr_0_19,substr ('2012-12-12 10:11:12 FFF',1, +) asSubstr_1_19,substr ('2012-12-12 10:11:12 FFF', +) asSubstr_19

Test statement result: Substr_0_20 and substr_1_19 results are consistent;substr_0_19 don't know why one less?

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

After a colleague's test, substr_0_20 can't get normal results on iOS.

Notes on the SUBSTR function of SQLite