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MAX(rowid) giving n+1 rows as answer

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-1

"SELECT max(rowid) from studdetail"
this should give maximum row in the table. And it is giving at one place but at another it is giving n+1(n is the no. of rows).
What can be the reasons?
I read something like hidden row is it that if yes then pls explain.
Thanks

mysql sqlite rowid

share|improve this question

asked Mar 25 at 16:30

HarshilHarshil

411 bronze badge

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  What does this mean? And it is giving at one place but at another
  
  – WEI_DBA
  Mar 25 at 16:31
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Which database? You have this tagged for multiple ones? I assume sqlite thanks to the use of the rowid column?
  
  – Shawn
  Mar 25 at 16:33
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  ""SELECT max(rowid) from studdetail" this should give maximum row in the table" It also assumes you never delete the "last" (max(rowid)) record from the table.. Also you are talking about SQLite because you are talking about rowid?
  
  – Raymond Nijland
  Mar 25 at 16:45
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Oh, wait. Are you expecting the max rowid to equal the number of rows in the table? That's not how things work.
  
  – Shawn
  Mar 25 at 18:18
  

  
  
  
  

add a comment | 

-1

"SELECT max(rowid) from studdetail"
this should give maximum row in the table. And it is giving at one place but at another it is giving n+1(n is the no. of rows).
What can be the reasons?
I read something like hidden row is it that if yes then pls explain.
Thanks

mysql sqlite rowid

share|improve this question

asked Mar 25 at 16:30

HarshilHarshil

411 bronze badge

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  What does this mean? And it is giving at one place but at another
  
  – WEI_DBA
  Mar 25 at 16:31
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Which database? You have this tagged for multiple ones? I assume sqlite thanks to the use of the rowid column?
  
  – Shawn
  Mar 25 at 16:33
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  ""SELECT max(rowid) from studdetail" this should give maximum row in the table" It also assumes you never delete the "last" (max(rowid)) record from the table.. Also you are talking about SQLite because you are talking about rowid?
  
  – Raymond Nijland
  Mar 25 at 16:45
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Oh, wait. Are you expecting the max rowid to equal the number of rows in the table? That's not how things work.
  
  – Shawn
  Mar 25 at 18:18
  

  
  
  
  

add a comment | 

"SELECT max(rowid) from studdetail"
this should give maximum row in the table. And it is giving at one place but at another it is giving n+1(n is the no. of rows).
What can be the reasons?
I read something like hidden row is it that if yes then pls explain.
Thanks

mysql sqlite rowid

share|improve this question

asked Mar 25 at 16:30

HarshilHarshil

411 bronze badge

share|improve this question

asked Mar 25 at 16:30

HarshilHarshil

411 bronze badge

share|improve this question

asked Mar 25 at 16:30

HarshilHarshil

411 bronze badge

asked Mar 25 at 16:30

HarshilHarshil

411 bronze badge

asked Mar 25 at 16:30

HarshilHarshil

411 bronze badge

1 Answer
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1

max(rowid) will return the highest rowid.

If rows have been deleted, or that rowid's have been skipped (can occur), or the rowid has been manually set, the highest allocated rowid may be greater than the number of actual rows. That is the rowid value for a row does not need to exactly represent it's position.

count(rowid) would return the number of rows.

Example

Consider the following :-

DROP TABLE IF EXISTS thetable;
CREATE TABLE IF NOT EXISTS thetable (mycolumn);
INSERT INTO thetable VALUES('A'),('B'),('C'),('D'),('E');
SELECT max(rowid), count(rowid) FROM thetable;
DELETE FROM thetable WHERE mycolumn = 'C';
SELECT max(rowid), count(rowid) FROM thetable;
INSERT INTO thetable (rowid,mycolumn) VALUES(26,'Z');
SELECT max(rowid), count(rowid) FROM thetable;

The first result, both max(rowid) and count(rowid) are 5 :-

The second result, as an intermediate row has been deleted, shows a discrepancy between the max(rowid) (5) and count(rowid) (4) :-

The third result, as a rowid value has been forced to be 26, shows an even greater discrepancy (26 v 5) :-

share|improve this answer

edited Mar 25 at 21:06

answered Mar 25 at 19:15

MikeTMikeT

21.7k1111 gold badges2828 silver badges4444 bronze badges

add a comment | 

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1

max(rowid) will return the highest rowid.

If rows have been deleted, or that rowid's have been skipped (can occur), or the rowid has been manually set, the highest allocated rowid may be greater than the number of actual rows. That is the rowid value for a row does not need to exactly represent it's position.

count(rowid) would return the number of rows.

Example

Consider the following :-

DROP TABLE IF EXISTS thetable;
CREATE TABLE IF NOT EXISTS thetable (mycolumn);
INSERT INTO thetable VALUES('A'),('B'),('C'),('D'),('E');
SELECT max(rowid), count(rowid) FROM thetable;
DELETE FROM thetable WHERE mycolumn = 'C';
SELECT max(rowid), count(rowid) FROM thetable;
INSERT INTO thetable (rowid,mycolumn) VALUES(26,'Z');
SELECT max(rowid), count(rowid) FROM thetable;

The first result, both max(rowid) and count(rowid) are 5 :-

The second result, as an intermediate row has been deleted, shows a discrepancy between the max(rowid) (5) and count(rowid) (4) :-

The third result, as a rowid value has been forced to be 26, shows an even greater discrepancy (26 v 5) :-

share|improve this answer

edited Mar 25 at 21:06

answered Mar 25 at 19:15

MikeTMikeT

21.7k1111 gold badges2828 silver badges4444 bronze badges

add a comment | 

1

max(rowid) will return the highest rowid.

If rows have been deleted, or that rowid's have been skipped (can occur), or the rowid has been manually set, the highest allocated rowid may be greater than the number of actual rows. That is the rowid value for a row does not need to exactly represent it's position.

count(rowid) would return the number of rows.

Example

Consider the following :-

DROP TABLE IF EXISTS thetable;
CREATE TABLE IF NOT EXISTS thetable (mycolumn);
INSERT INTO thetable VALUES('A'),('B'),('C'),('D'),('E');
SELECT max(rowid), count(rowid) FROM thetable;
DELETE FROM thetable WHERE mycolumn = 'C';
SELECT max(rowid), count(rowid) FROM thetable;
INSERT INTO thetable (rowid,mycolumn) VALUES(26,'Z');
SELECT max(rowid), count(rowid) FROM thetable;

The first result, both max(rowid) and count(rowid) are 5 :-

The second result, as an intermediate row has been deleted, shows a discrepancy between the max(rowid) (5) and count(rowid) (4) :-

The third result, as a rowid value has been forced to be 26, shows an even greater discrepancy (26 v 5) :-

share|improve this answer

edited Mar 25 at 21:06

answered Mar 25 at 19:15

MikeTMikeT

21.7k1111 gold badges2828 silver badges4444 bronze badges

add a comment | 

max(rowid) will return the highest rowid.

If rows have been deleted, or that rowid's have been skipped (can occur), or the rowid has been manually set, the highest allocated rowid may be greater than the number of actual rows. That is the rowid value for a row does not need to exactly represent it's position.

count(rowid) would return the number of rows.

Example

Consider the following :-

DROP TABLE IF EXISTS thetable;
CREATE TABLE IF NOT EXISTS thetable (mycolumn);
INSERT INTO thetable VALUES('A'),('B'),('C'),('D'),('E');
SELECT max(rowid), count(rowid) FROM thetable;
DELETE FROM thetable WHERE mycolumn = 'C';
SELECT max(rowid), count(rowid) FROM thetable;
INSERT INTO thetable (rowid,mycolumn) VALUES(26,'Z');
SELECT max(rowid), count(rowid) FROM thetable;

The first result, both max(rowid) and count(rowid) are 5 :-

The second result, as an intermediate row has been deleted, shows a discrepancy between the max(rowid) (5) and count(rowid) (4) :-

The third result, as a rowid value has been forced to be 26, shows an even greater discrepancy (26 v 5) :-

share|improve this answer

edited Mar 25 at 21:06

answered Mar 25 at 19:15

MikeTMikeT

21.7k1111 gold badges2828 silver badges4444 bronze badges

DROP TABLE IF EXISTS thetable;
CREATE TABLE IF NOT EXISTS thetable (mycolumn);
INSERT INTO thetable VALUES('A'),('B'),('C'),('D'),('E');
SELECT max(rowid), count(rowid) FROM thetable;
DELETE FROM thetable WHERE mycolumn = 'C';
SELECT max(rowid), count(rowid) FROM thetable;
INSERT INTO thetable (rowid,mycolumn) VALUES(26,'Z');
SELECT max(rowid), count(rowid) FROM thetable;

share|improve this answer

edited Mar 25 at 21:06

answered Mar 25 at 19:15

MikeTMikeT

21.7k1111 gold badges2828 silver badges4444 bronze badges

answered Mar 25 at 19:15

MikeTMikeT

21.7k1111 gold badges2828 silver badges4444 bronze badges

answered Mar 25 at 19:15

MikeTMikeT

21.7k1111 gold badges2828 silver badges4444 bronze badges