[sqlite] Why TRUNCATE TABLE can't empty a table?

[daedae11]

Following is my program:
rc = sqlite3_exec(db, TRUNCATE TABLE students;, NULL, NULL, errMsg);

but this sentence can success and return 1.
Help~
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[sqlite] How to recognize a sqlite database file?

[daedae11]

How can I judge whether a file is a database file? Is there a function that I 
can use for this purpose?
Help! 
Hope for you  reply.
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Re: [sqlite] How to recognize a sqlite database file?

[daedae11]

Thank you. I got it. And I have another question. Does function sqlite3_exec 
support UTF-16?





At 2012-08-14 10:01:13,Simon Slavin slav...@bigfraud.org wrote:

On 14 Aug 2012, at 2:57am, daedae11 daeda...@126.com wrote:

 How can I judge whether a file is a database file? Is there a function that 
 I can use for this purpose?

You can use the SQLite library call to open it and see whether you get an 
error back.  But it might be better to open the file as binary/text and read 
the beginning of it.  All SQLite files begin with

SQLite format 3

and then a 0x00 character.  Of course, there's nothing to stop someone writing 
such a file themself but it would have to be a joke.  See

http://www.sqlite.org/fileformat.html

Simon.
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Re: [sqlite] How to recognize a sqlite database file?

[daedae11]

If I use the group of:
sqlite3_prepare16_v2()
sqlite3_step()
andsqlite3_finalize()

how can I get the names of a table's columns from a SELECT sql sentence?




At 2012-08-14 10:11:31,Simon Slavin slav...@bigfraud.org wrote:

On 14 Aug 2012, at 3:05am, daedae11 daeda...@126.com wrote:

 Thank you. I got it. And I have another question. Does function sqlite3_exec 
 support UTF-16?

No.  sqlite3_exec() is a wrapper around sqlite3_prepare_v2(), and 
sqlite3_prepare_v2() expects UTF-8.  For UTF-16 you should be using 
sqlite3_prepare16_v2() .  But for some reason there's no sqlite3_exec16() .

However, _exec is relatively simple to write.  You can see what it does here:

http://sqlite.org/c3ref/exec.html

So all you should need to do is

sqlite3_prepare16_v2()
sqlite3_step()
andsqlite3_finalize()

Good luck with it.

Simon.
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Re: [sqlite] How to recognize a sqlite database file?

[daedae11]

Thank you. And I found these functions:

const char *sqlite3_column_database_name(sqlite3_stmt*,int);
const void *sqlite3_column_database_name16(sqlite3_stmt*,int);
const char *sqlite3_column_table_name(sqlite3_stmt*,int);
const void *sqlite3_column_table_name16(sqlite3_stmt*,int);
const char *sqlite3_column_origin_name(sqlite3_stmt*,int);
const void *sqlite3_column_origin_name16(sqlite3_stmt*,int);

maybe it's more convenient.





At 2012-08-14 11:44:14,Igor Tandetnik itandet...@mvps.org wrote:
daedae11 daeda...@126.com wrote:
 If I use the group of:
 sqlite3_prepare16_v2()
 sqlite3_step()
 andsqlite3_finalize()
 
 how can I get the names of a table's columns from a SELECT sql sentence?

sqlite3_column_name[16]

-- 
Igor Tandetnik

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