What does select count 1 from table name on any database tables mean

Question

When we execute select count    from table name it returns the number of rows   What does count 1  do  What does 1 signify here  Is this the same as count     as it gives the same result on execution

User · Answer

Depending on who you ask  some people report that executing select count 1  from random table  runs faster than select count    from random table  Others claim they are exactly the same   This link claims that the speed difference between the 2 is due to a FULL TABLE SCAN vs FAST FULL SCAN

User · Answer

This is similar to the difference between   SELECT   FROM table name and SELECT 1 FROM table name      If you do   SELECT 1 FROM table name   it will give you the number 1 for each row in the table   So yes count    and count 1  will provide the same results as will count 8  or count column name

User · Answer

in oracle i believe these have exactly the same meaning

User · Answer

Difference between count    and count 1  in oracle   count    means it will count all records i e each and every cell BUT  count 1  means it will add one pseudo column with value 1 and returns count of all records

User · Answer

Depending on who you ask  some people report that executing select count 1  from random table  runs faster than select count    from random table  Others claim they are exactly the same   This link claims that the speed difference between the 2 is due to a FULL TABLE SCAN vs FAST FULL SCAN

User · Answer

You can test like this   create table test1   id number   name varchar2 20      insert into test1 values  1  abc    insert into test1 values  1  abc     select   from test1  select count    from test1  select count 1  from test1  select count ALL 1  from test1  select count DISTINCT 1  from test1

User · Answer

in oracle i believe these have exactly the same meaning

User · Answer

Here is a link that will help answer your questions  In short      count    is the correct way to write   it and count 1  is OPTIMIZED TO BE   count     internally -- since       a  count the rows where 1 is not null   is less efficient than   b  count the rows

User · Answer

Depending on who you ask  some people report that executing select count 1  from random table  runs faster than select count    from random table  Others claim they are exactly the same   This link claims that the speed difference between the 2 is due to a FULL TABLE SCAN vs FAST FULL SCAN

User · Answer

The parameter to the COUNT function is an expression that is to be evaluated for each row  The COUNT function returns the number of rows for which the expression evaluates to a non-null value      is a special expression that is not evaluated  it simply returns the number of rows    There are two additional modifiers for the expression  ALL and DISTINCT  These determine whether duplicates are discarded  Since ALL is the default  your example is the same as count ALL 1   which means that duplicates are retained   Since the expression  1  evaluates to non-null for every row  and since you are not removing duplicates  COUNT 1  should always return the same number as COUNT

User · Answer

in oracle i believe these have exactly the same meaning

User · Answer

in oracle i believe these have exactly the same meaning

User · Answer

There is no difference   COUNT 1  is basically just counting a constant value 1 column for each row   As other users here have said  it s the same as COUNT 0  or COUNT 42    Any non-NULL value will suffice   http   asktom oracle com pls asktom f p 100 11 2603224624843292    P11 QUESTION ID 1156151916789  The Oracle optimizer did apparently use to have bugs in it  which caused the count to be affected by which column you picked and whether it was in an index  so the COUNT 1  convention came into being

User · Answer

Here is a link that will help answer your questions  In short      count    is the correct way to write   it and count 1  is OPTIMIZED TO BE   count     internally -- since       a  count the rows where 1 is not null   is less efficient than   b  count the rows

User · Answer

Here is a link that will help answer your questions  In short      count    is the correct way to write   it and count 1  is OPTIMIZED TO BE   count     internally -- since       a  count the rows where 1 is not null   is less efficient than   b  count the rows

User · Answer

SELECT COUNT 1  from  lt table name gt    should do the exact same thing as   SELECT COUNT     from  lt table name gt    There may have been or still be some reasons why it would perform better than SELECT COUNT   on some database  but I would consider that a bug in the DB   SELECT COUNT col name  from  lt table name gt    however has a different meaning  as it counts only the rows with a non-null value for the given column

User · Answer

SELECT COUNT 1  from  lt table name gt    should do the exact same thing as   SELECT COUNT     from  lt table name gt    There may have been or still be some reasons why it would perform better than SELECT COUNT   on some database  but I would consider that a bug in the DB   SELECT COUNT col name  from  lt table name gt    however has a different meaning  as it counts only the rows with a non-null value for the given column

User · Answer

The parameter to the COUNT function is an expression that is to be evaluated for each row  The COUNT function returns the number of rows for which the expression evaluates to a non-null value      is a special expression that is not evaluated  it simply returns the number of rows    There are two additional modifiers for the expression  ALL and DISTINCT  These determine whether duplicates are discarded  Since ALL is the default  your example is the same as count ALL 1   which means that duplicates are retained   Since the expression  1  evaluates to non-null for every row  and since you are not removing duplicates  COUNT 1  should always return the same number as COUNT

User · Answer

There is no difference   COUNT 1  is basically just counting a constant value 1 column for each row   As other users here have said  it s the same as COUNT 0  or COUNT 42    Any non-NULL value will suffice   http   asktom oracle com pls asktom f p 100 11 2603224624843292    P11 QUESTION ID 1156151916789  The Oracle optimizer did apparently use to have bugs in it  which caused the count to be affected by which column you picked and whether it was in an index  so the COUNT 1  convention came into being

User · Answer

This is similar to the difference between   SELECT   FROM table name and SELECT 1 FROM table name      If you do   SELECT 1 FROM table name   it will give you the number 1 for each row in the table   So yes count    and count 1  will provide the same results as will count 8  or count column name

User · Answer

Depending on who you ask  some people report that executing select count 1  from random table  runs faster than select count    from random table  Others claim they are exactly the same   This link claims that the speed difference between the 2 is due to a FULL TABLE SCAN vs FAST FULL SCAN

User · Answer

Difference between count    and count 1  in oracle   count    means it will count all records i e each and every cell BUT  count 1  means it will add one pseudo column with value 1 and returns count of all records

User · Answer

Here is a link that will help answer your questions  In short      count    is the correct way to write   it and count 1  is OPTIMIZED TO BE   count     internally -- since       a  count the rows where 1 is not null   is less efficient than   b  count the rows

User · Answer

There is no difference   COUNT 1  is basically just counting a constant value 1 column for each row   As other users here have said  it s the same as COUNT 0  or COUNT 42    Any non-NULL value will suffice   http   asktom oracle com pls asktom f p 100 11 2603224624843292    P11 QUESTION ID 1156151916789  The Oracle optimizer did apparently use to have bugs in it  which caused the count to be affected by which column you picked and whether it was in an index  so the COUNT 1  convention came into being

User · Answer

You can test like this   create table test1   id number   name varchar2 20      insert into test1 values  1  abc    insert into test1 values  1  abc     select   from test1  select count    from test1  select count 1  from test1  select count ALL 1  from test1  select count DISTINCT 1  from test1

User · Answer

Difference between count    and count 1  in oracle   count    means it will count all records i e each and every cell BUT  count 1  means it will add one pseudo column with value 1 and returns count of all records

User · Answer

SELECT COUNT 1  from  lt table name gt    should do the exact same thing as   SELECT COUNT     from  lt table name gt    There may have been or still be some reasons why it would perform better than SELECT COUNT   on some database  but I would consider that a bug in the DB   SELECT COUNT col name  from  lt table name gt    however has a different meaning  as it counts only the rows with a non-null value for the given column

User · Answer

This is similar to the difference between   SELECT   FROM table name and SELECT 1 FROM table name      If you do   SELECT 1 FROM table name   it will give you the number 1 for each row in the table   So yes count    and count 1  will provide the same results as will count 8  or count column name

User · Answer

This is similar to the difference between   SELECT   FROM table name and SELECT 1 FROM table name      If you do   SELECT 1 FROM table name   it will give you the number 1 for each row in the table   So yes count    and count 1  will provide the same results as will count 8  or count column name

User · Answer

The parameter to the COUNT function is an expression that is to be evaluated for each row  The COUNT function returns the number of rows for which the expression evaluates to a non-null value      is a special expression that is not evaluated  it simply returns the number of rows    There are two additional modifiers for the expression  ALL and DISTINCT  These determine whether duplicates are discarded  Since ALL is the default  your example is the same as count ALL 1   which means that duplicates are retained   Since the expression  1  evaluates to non-null for every row  and since you are not removing duplicates  COUNT 1  should always return the same number as COUNT

User · Answer

There is no difference   COUNT 1  is basically just counting a constant value 1 column for each row   As other users here have said  it s the same as COUNT 0  or COUNT 42    Any non-NULL value will suffice   http   asktom oracle com pls asktom f p 100 11 2603224624843292    P11 QUESTION ID 1156151916789  The Oracle optimizer did apparently use to have bugs in it  which caused the count to be affected by which column you picked and whether it was in an index  so the COUNT 1  convention came into being

User · Answer

SELECT COUNT 1  from  lt table name gt    should do the exact same thing as   SELECT COUNT     from  lt table name gt    There may have been or still be some reasons why it would perform better than SELECT COUNT   on some database  but I would consider that a bug in the DB   SELECT COUNT col name  from  lt table name gt    however has a different meaning  as it counts only the rows with a non-null value for the given column

User · Answer

The parameter to the COUNT function is an expression that is to be evaluated for each row  The COUNT function returns the number of rows for which the expression evaluates to a non-null value      is a special expression that is not evaluated  it simply returns the number of rows    There are two additional modifiers for the expression  ALL and DISTINCT  These determine whether duplicates are discarded  Since ALL is the default  your example is the same as count ALL 1   which means that duplicates are retained   Since the expression  1  evaluates to non-null for every row  and since you are not removing duplicates  COUNT 1  should always return the same number as COUNT

User · Answer

Difference between count    and count 1  in oracle   count    means it will count all records i e each and every cell BUT  count 1  means it will add one pseudo column with value 1 and returns count of all records

[sql] What does "select count(1) from table_name" on any database tables mean?

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