Re: [sqlite] Why does the FAQ example use 2 copies for adding/deleting a column

[drh]

Lothar Scholz <[EMAIL PROTECTED]> wrote:
> Hello,
> 
> The example for question 11 in the FAQ has this code for dropping an
> existing table column 'c'
> 
> BEGIN TRANSACTION;
> CREATE TEMPORARY TABLE t1_backup(a,b);
> INSERT INTO t1_backup SELECT a,b FROM t1;
> DROP TABLE t1;
> CREATE TABLE t1(a,b);
> INSERT INTO t1 SELECT a,b FROM t1_backup;
> DROP TABLE t1_backup;
> COMMIT;
> 
> This is copying the whole table twice. Is there any reason why it
> shouldn't be:
> 
> BEGIN TRANSACTION;
> CREATE TEMPORARY TABLE t1_backup(a,b);
> INSERT INTO t1_backup SELECT a,b FROM t1;
> DROP TABLE t1;
> ALTER TABLE t1_backup RENAME TO t1;
> COMMIT;
> 
> Or is this just that ALTER TABLE RENAME did not exist when the FAQ was
> created?
> 

The latter.
--
D. Richard Hipp <[EMAIL PROTECTED]>


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[sqlite] Why does the FAQ example use 2 copies for adding/deleting a column

[Lothar Scholz]

Hello,

The example for question 11 in the FAQ has this code for dropping an
existing table column 'c'

BEGIN TRANSACTION;
CREATE TEMPORARY TABLE t1_backup(a,b);
INSERT INTO t1_backup SELECT a,b FROM t1;
DROP TABLE t1;
CREATE TABLE t1(a,b);
INSERT INTO t1 SELECT a,b FROM t1_backup;
DROP TABLE t1_backup;
COMMIT;

This is copying the whole table twice. Is there any reason why it
shouldn't be:

BEGIN TRANSACTION;
CREATE TEMPORARY TABLE t1_backup(a,b);
INSERT INTO t1_backup SELECT a,b FROM t1;
DROP TABLE t1;
ALTER TABLE t1_backup RENAME TO t1;
COMMIT;

Or is this just that ALTER TABLE RENAME did not exist when the FAQ was
created?



-- 
Best regards,
 Lothar Scholz  mailto:[EMAIL PROTECTED]


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