Re: [sqlite] how to get the meta type of a column

[gujx]

>If all you have is a void*, you're going to have a very hard time calling
any sqlite3_bind_*() function. 
yes, I just have all values with the type void*, so I can not choose which
sqlite3_bind_*() functions to use.





Jay A. Kreibich-2 wrote:
> 
> On Thu, Feb 04, 2010 at 06:41:46PM -0800, gujx scratched on the wall:
>> 
>> Maybe I didn't express the problem clearly.
>> > e.g. if you have a text value, you use _text(), if you have an int, you
>> > use _int()
> 
>> I just don't know what type I have,
> 
>   If all you have is a void*, you're going to have a very hard time
>   calling any sqlite3_bind_*() function.  I sure hope you know what YOU
>   have, you're just not sure about the place you want to stick it.
> 
>> so I want to get the meta type of the column somebody defined.
> 
>   One more time: columns don't have types.  There is no way to get the
>   affinity (that I'm aware of) other than replicating code internal to
>   SQLite.  Asking again won't change this.
> 
>> e.g. I'd like to use a bind routine to bind a variable t to a "?", but I
>> don't konw this t is a string or a number or it is a object,
> 
>   It doesn't matter.
> 
>> so I want to
>> know that the table is defined like "id(varchar)" ,then I will use
>> sqlite3_bind_text; or it is defined like "id(integer)", then I will
>> choose
>> sqlite3_bind_int.
> 
>   I understand that, but you need to put something in the third
>   parameter.  If you're going to call sqlite3_bind_text(), you need a
>   const char * for the third parameter.  If you're going to call 
>   sqlite3_bind_int(), you need an int for the third parameter.  What
>   you have, in your C code, will best dictate what bind function to
>   use.  SQLite will then do any conversions required, given the column
>   affinity, and it is generally going to do a better and smarter job
>   than your code can because it has more information about what is
>   going on.
> 
>> >  http://sqlite.org/datatype3.html
>> >  
>> >   Read this whole page.  Several times.  Make sure you understand it in
>> >   great detail.
> 
>-j
> 
> -- 
> Jay A. Kreibich < J A Y  @  K R E I B I.C H >
> 
> "Our opponent is an alien starship packed with atomic bombs.  We have
>  a protractor."   "I'll go home and see if I can scrounge up a ruler
>  and a piece of string."  --from Anathem by Neal Stephenson
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> 

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Re: [sqlite] how to get the meta type of a column

[gujx]

Maybe I didn't express the problem clearly.
> e.g. if you have a text value, you use _text(), if you have an int, you
> use _int()
I just don't know what type I have, so I want to get the meta type of the
column somebody defined.
e.g. I'd like to use a bind routine to bind a variable t to a "?", but I
don't konw this t is a string or a number or it is a object, so I want to
know that the table is defined like "id(varchar)" ,then I will use
sqlite3_bind_text; or it is defined like "id(integer)", then I will choose
sqlite3_bind_int.


Jay A. Kreibich-2 wrote:
> 
> On Thu, Feb 04, 2010 at 03:59:14PM +0800, gujx scratched on the wall:
>> There is a table like this:
> 
> 
>> Is there any way to resolve this?
> 
>   First off, you need to understand that columns do not have "types",
>   they have affinities.
> 
>  http://sqlite.org/datatype3.html
>  
>   Read this whole page.  Several times.  Make sure you understand it in
>   great detail.
> 
> 
> 
>   Second, you can put any type into (almost) any column, so it doesn't
>   matter.  If the affinity is setup right, SQLite will usually do the
>   right thing.  For example, if you have a column with numeric affinity
>   and you insert the text value '12', it will converted to an integer
>   before it is stored.
> 
>   Which bind function you use is usually dictated by what you have
>   (e.g. if you have a text value, you use _text(), if you have an int,
>   you use _int()), rather than the column you are placing it in. 
>   SQLite will try its best to convert what you've given it into a
>   format that makes sense for the column, but if it can't, it will store
>   it in whatever format you sent.  Which is more or less exactly the
>   position you'd be in if you wanted to do the conversion "by-hand."
> 
>-j
> 
> -- 
> Jay A. Kreibich < J A Y  @  K R E I B I.C H >
> 
> "Our opponent is an alien starship packed with atomic bombs.  We have
>  a protractor."   "I'll go home and see if I can scrounge up a ruler
>  and a piece of string."  --from Anathem by Neal Stephenson
> ___
> sqlite-users mailing list
> sqlite-users@sqlite.org
> http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
> 
> 

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[sqlite] how to get the meta type of a column

[gujx]

There is a table like this:


id(varchar)

name(text)

age(integer)

ss(text)

Its name is “test_for_cpp”, now I get the pointer of sqlite successfully. 

 

There are codes below:

 

sqlite3_stmt *ppStmt;

const char *pzTail; 

int nVal = sqlite3_prepare_v2(

   conn,   

   "INSERT INTO [test_for_cpp] ([id], [name], [age], [ss]) VALUES (?, ?,
?, ’exa’) ; ", 

   -1,

   ,  

   

);

 

now, I should use routines such as
 sqlite3_bind_text to bind data
with the “?”, but I don’t know the exact meta type of the column. 

I don’t know that the meta type of the column id is “integer”, and I
don’t know the meta type of the column name is “text”.…… So, I can’t
choose the exact bind routine.

Is there any way to resolve this?

 

 

 

Gu Jinxiang

 

以上、よろしくお��いします。

 

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[sqlite] how to get the type of a parameter

[gujx]

Hi, I had a question puzzled me. How can I get the type of a parameter in a
prepared SQL.

For example, the code is:

 

sqlite3 *conn;

if (SQLITE_OK != sqlite3_open("testBind.db", ))

{

   printf("can't open the database.");

   return ;

}

 

if(SQLITE_OK != sqlite3_exec(conn, "create table  test_for_cpp(id
integer,name text,age integer)", 0, 0, 0))

{

   return ;

}

 

   sqlite3_stmt *ppStmt;

const char *pzTail; 

int nVal =sqlite3_prepare_v2(

   conn,   

   "INSERT INTO [test_for_cpp] ([id], [age], [name]) VALUES (?, ?,
'xiaowang') ; ",

   -1,

   ,  

   

);

 

 

How can I get the type of the specific column that a “?” referenced to?
For example, I want to get the type (here is integer) of the first column
that the first “?” referenced to.

 

 

Gu Jinxiang

 

以上、よろしくお��いします。

 

 

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[sqlite] how to get the type of a parameter

[gujx]

Hi, I had a question puzzled me. How can I get the type of a parameter in a
prepared SQL.

For example, the code is:

 

sqlite3 *conn;

if (SQLITE_OK != sqlite3_open("testBind.db", ))

{

   printf("can't open the database.");

   return ;

}

 

if(SQLITE_OK != sqlite3_exec(conn, "create table  test_for_cpp(id
integer,name text,age integer)", 0, 0, 0))

{

   return ;

}

 

   sqlite3_stmt *ppStmt;

const char *pzTail; 

int nVal =sqlite3_prepare_v2(

   conn,   

   "INSERT INTO [test_for_cpp] ([id], [age], [name]) VALUES (?, ?,
'xiaowang') ; ",

   -1,

   ,  

   

);

 

 

How can I get the type of the specific column that a “?” referenced to?
For example, I want to get the type (here is integer) of the first column
that the first “?” referenced to.

 

Gu Jinxiang

 

以上、よろしくお��いします。

 

 

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[sqlite] size control of sqlite database

[gujx]

Hi, I’d like to ask some question about the interface of the sqlite
resource.

Whether there is some interface to control the size of a database, for
example, if I want to create a database with 5M initialized, how can I do
that? And when I make change to a database, for example, insert a row to a
table, then can I get the size of the database now?

 

Looking forward to your answer.

 

 

Gu Jinxiang

 

以上、よろしくお��いします。

 

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