Re: [sqlite] To use or not to use single quotes with integers

[Simon Slavin]

On 12 Apr 2018, at 7:49pm, Thomas Kurz  wrote:

> [Simon Slavin wrote]
> 
>> A similar thing happens when you specify that a column has affinity of REAL. 
>>  In both cases, SQLite considers that the CREATE command knows better than 
>> whatever specifies the value, and does the conversion.  However for the 
>> number to be stored the conversion has to be reversible.  If SQLite reverses 
>> the conversion and doesn't get the original string back it stores the string 
>> instead.
> 
> I don't think this is actually the case:
> 
> create table test (i integer, r real, s text);
> insert into test (i, r, s) values (3.141592653589793238462643, 
> 3.141592653589793238462643, 3.141592653589793238462643);
> insert into test (i, r, s) values ('3.141592653589793238462643', 
> '3.141592653589793238462643', '3.141592653589793238462643');
> select * from test;
> 
> In any case except of actually storing the string to column s, I get the 
> stored value truncated to 14 decimals.

From the above data (nice test dataset, by the way):

sqlite> SELECT i,typeof(i) FROM test;
3.14159265358979|real
3.14159265358979|real
sqlite> SELECT r,typeof(r) FROM test;
3.14159265358979|real
3.14159265358979|real
sqlite> SELECT s,typeof(s) FROM test;
3.14159265358979|text
3.141592653589793238462643|text

Where you specified that you wanted a string stored and provided a string in 
the INSERT command, SQLite stored a string.  In all other cases SQLite had to 
handle the value as a number at some point in the storage process, and it 
turned it into a floating point value as long as its floating point library can 
handle.  Since it would have to reduce the precision in this way before doing 
any mathematical operation on the resulting value, this counts as 'identical 
and reversible'.

Simon.
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Re: [sqlite] To use or not to use single quotes with integers

[David Raymond]

http://www.sqlite.org/datatype3.html#type_affinity

The key sentence in that section is
"SQLite considers the conversion to be lossless and reversible if the first 15 
significant decimal digits of the number are preserved"


-Original Message-
From: sqlite-users [mailto:sqlite-users-boun...@mailinglists.sqlite.org] On 
Behalf Of Thomas Kurz
Sent: Thursday, April 12, 2018 2:50 PM
To: SQLite mailing list
Subject: Re: [sqlite] To use or not to use single quotes with integers

Dear Simon,

> A similar thing happens when you specify that a column has affinity of REAL.  
> In both cases, SQLite considers that the CREATE command knows better than 
> whatever specifies the value, and does the conversion.  However for the 
> number to be stored the conversion has to be reversible.  If SQLite reverses 
> the conversion and doesn't get the original string back it stores the string 
> instead.

I don't think this is actually the case:

create table test (i integer, r real, s text);
insert into test (i, r, s) values (3.141592653589793238462643, 
3.141592653589793238462643, 3.141592653589793238462643);
insert into test (i, r, s) values ('3.141592653589793238462643', 
'3.141592653589793238462643', '3.141592653589793238462643');
select * from test;

In any case except of actually storing the string to column s, I get the stored 
value truncated to 14 decimals.

select cast(s as text) from test;

Even here, the first value is truncated to 14 decimals. Only the 2nd is correct.

Kind regards,
Thomas

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Re: [sqlite] To use or not to use single quotes with integers

[Thomas Kurz]

Dear Simon,

> A similar thing happens when you specify that a column has affinity of REAL.  
> In both cases, SQLite considers that the CREATE command knows better than 
> whatever specifies the value, and does the conversion.  However for the 
> number to be stored the conversion has to be reversible.  If SQLite reverses 
> the conversion and doesn't get the original string back it stores the string 
> instead.

I don't think this is actually the case:

create table test (i integer, r real, s text);
insert into test (i, r, s) values (3.141592653589793238462643, 
3.141592653589793238462643, 3.141592653589793238462643);
insert into test (i, r, s) values ('3.141592653589793238462643', 
'3.141592653589793238462643', '3.141592653589793238462643');
select * from test;

In any case except of actually storing the string to column s, I get the stored 
value truncated to 14 decimals.

select cast(s as text) from test;

Even here, the first value is truncated to 14 decimals. Only the 2nd is correct.

Kind regards,
Thomas

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Re: [sqlite] To use or not to use single quotes with integers

[Markos]

Thanks Simon and David for your attention,
Markos



Insert the usual "Bobby Tables" reply here
https://xkcd.com/327/

You really want to just bind the values to the insert statement, both to 
prevent issues and make things simpler. It'll look slightly different in each 
language, but it's basically 1 SQL statement text which contains placeholders. 
Then for each record you want to insert/update, etc you give it the raw values 
separate from the SQL text, and your language of choice will do the magic of 
inserting that exact value, whatever type of value that is.

So it might look something like:

myInsertStatement = "insert into foods (name, type_id) values (?, ?);"
for some looping construct:
nameVariable = some name
type_idVariable = some ID thing of whatever type
databaseCursor.execute(myInsertStatement, nameVariable, type_idVariable)
databaseConnection.commit()



Em 08-04-2018 14:03, Simon Slavin escreveu:

On 8 Apr 2018, at 11:54am, Markos  wrote:


CREATE TABLE foods(
  id integer PRIMARY KEY,
  type_id integer,
  name text );

I can insert type_id without single quote:

INSERT INTO foods (name, type_id) VALUES ('Rice', 16);

And also with single quote:

INSERT INTO foods (name, type_id) VALUES ('Bean', '17');

select * FROM foods;

...
423 16  Rice
424 17  Bean

What are the consequences of inserting values in fields of datatype integer 
with single quotes?

Well done for testing what happens rather than just assuming things worked the 
way you thought.

When you created the table you specified the affinity of each column.  If you 
define a column as INTEGER but supply a string, SQLite checks to see whether 
that string represents an integer.  If it does, then it stores the integer, 
effectively doing the translation for you.  The actual value stored is integer, 
and there is no trace that it was originally specified as a string.

A similar thing happens when you specify that a column has affinity of REAL.  
In both cases, SQLite considers that the CREATE command knows better than 
whatever specifies the value, and does the conversion.  However for the number 
to be stored the conversion has to be reversible.  If SQLite reverses the 
conversion and doesn't get the original string back it stores the string 
instead.

You can test to see what SQLite did using

 SELECT id, type_id, typeof(type_id), name FROM foods

See section 3 (more usefully, the entire page) of



Simon.
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Re: [sqlite] To use or not to use single quotes with integers

[David Raymond]

Insert the usual "Bobby Tables" reply here
https://xkcd.com/327/

You really want to just bind the values to the insert statement, both to 
prevent issues and make things simpler. It'll look slightly different in each 
language, but it's basically 1 SQL statement text which contains placeholders. 
Then for each record you want to insert/update, etc you give it the raw values 
separate from the SQL text, and your language of choice will do the magic of 
inserting that exact value, whatever type of value that is.

So it might look something like:

myInsertStatement = "insert into foods (name, type_id) values (?, ?);"
for some looping construct:
nameVariable = some name
type_idVariable = some ID thing of whatever type
databaseCursor.execute(myInsertStatement, nameVariable, type_idVariable)
databaseConnection.commit()

-Original Message-
From: sqlite-users [mailto:sqlite-users-boun...@mailinglists.sqlite.org] On 
Behalf Of Markos
Sent: Sunday, April 08, 2018 6:54 AM
To: sqlite-users@mailinglists.sqlite.org
Subject: [sqlite] To use or not to use single quotes with integers


I'm making this question because it is simpler to implement in my 
interface a routine to assemble a list of fields and values by inserting 
single quotation marks in all elements of the list of values.

Otherwise I would have to identify the datatype of each field to decide 
whether or not to include the quotes.

Thank you,
Markos

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Re: [sqlite] To use or not to use single quotes with integers

[Simon Slavin]

On 8 Apr 2018, at 11:54am, Markos  wrote:

> CREATE TABLE foods(
>  id integer PRIMARY KEY,
>  type_id integer,
>  name text );
> 
> I can insert type_id without single quote:
> 
> INSERT INTO foods (name, type_id) VALUES ('Rice', 16);
> 
> And also with single quote:
> 
> INSERT INTO foods (name, type_id) VALUES ('Bean', '17');
> 
> select * FROM foods;
> 
> ...
> 423 16  Rice
> 424 17  Bean
> 
> What are the consequences of inserting values in fields of datatype integer 
> with single quotes?

Well done for testing what happens rather than just assuming things worked the 
way you thought.

When you created the table you specified the affinity of each column.  If you 
define a column as INTEGER but supply a string, SQLite checks to see whether 
that string represents an integer.  If it does, then it stores the integer, 
effectively doing the translation for you.  The actual value stored is integer, 
and there is no trace that it was originally specified as a string.

A similar thing happens when you specify that a column has affinity of REAL.  
In both cases, SQLite considers that the CREATE command knows better than 
whatever specifies the value, and does the conversion.  However for the number 
to be stored the conversion has to be reversible.  If SQLite reverses the 
conversion and doesn't get the original string back it stores the string 
instead.

You can test to see what SQLite did using

SELECT id, type_id, typeof(type_id), name FROM foods

See section 3 (more usefully, the entire page) of



Simon.
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[sqlite] To use or not to use single quotes with integers

[Markos]

Hi,

I'm a beginner with sqliteand used to insert values in the fields of 
datatype text with single quote and values of datatype integer without 
single quote.


But I realized that sqlite accepts inserting both data types (text and 
integer) with single quote without error.


For example the table:

CREATE TABLE foods(
  id integer PRIMARY KEY,
  type_id integer,
  name text );

I can insert type_id without single quote:

INSERT INTO foods (name, type_id) VALUES ('Rice', 16);

And also with single quote:

INSERT INTO foods (name, type_id) VALUES ('Bean', '17');

select * FROM foods;

...
423 16  Rice
424 17  Bean

What are the consequences of inserting values in fields of datatype 
integer with single quotes?


What are the effects on database size and performance?

Can I have problems in the future to make a query using logical 
operators in these fields?


I'm making this question because it is simpler to implement in my 
interface a routine to assemble a list of fields and values by inserting 
single quotation marks in all elements of the list of values.


Otherwise I would have to identify the datatype of each field to decide 
whether or not to include the quotes.


Thank you,
Markos

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