MySQL What s the difference between float and double

Question

Checking in the new database structure I saw that someone changed a field from float to double  Wondering why  I checked the mysql documentation  but honestly didn t understand what the difference is   Can someone explain

User · Answer

Doubles are just like floats  except for the fact that they are twice as large  This allows for a greater accuracy

User · Answer

FLOAT stores floating point numbers with accuracy up to eight places and has four bytes while DOUBLE stores floating point numbers with accuracy upto 18 places and has eight bytes

User · Answer

Thought I d add my own example that helped me see the difference using the value 1 3 when adding or multiplying with another float  decimal  and double    1 3 float ADDED to 1 3 of different types    float                double   decimal    ------------------- ------------ -----   2 5999999046325684   2 6      2 60000     1 3 float MULTIPLIED by 1 3 of different types     float                double               decimal         -------------------- -------------------- --------------    1 6899998760223411   1 6900000000000002   1 6900000000     This is using MySQL 6 7  Query   SELECT      float 1   float 2 as  float add       double 1   double 2 as  double add       decimal 1   decimal 2 as  decimal add        float 1   float 2 as  float multiply       double 1   double 2 as  double multiply       decimal 1   decimal 2 as  decimal multiply  FROM numerics   Create Table and Insert Data   CREATE TABLE  numerics       float 1  float DEFAULT NULL     float 2  float DEFAULT NULL     double 1  double DEFAULT NULL     double 2  double DEFAULT NULL     decimal 1  decimal 10 5  DEFAULT NULL     decimal 2  decimal 10 5  DEFAULT NULL   ENGINE InnoDB DEFAULT CHARSET utf8   INSERT INTO   numerics                  float 1            float 2            double 1            double 2            decimal 1            decimal 2        VALUES               1 3          1 3          1 3          1 3          1 30000          1 30000

User · Answer

Perhaps this example could explain  CREATE TABLE  test   fla  FLOAT  flb  FLOAT  dba  DOUBLE 10 2   dbb  DOUBLE 10 2      We have a table like this   ------- -------------    Field   Type           ------- -------------    fla     float           flb     float           dba     double 10 2     dbb     double 10 2    ------- -------------   For first difference  we try to insert a record with  1 2  to each field  INSERT INTO  test  values  1 2 1 2 1 2 1 2    The table showing like this  SELECT   FROM  test     ------ ------ ------ ------    fla    flb    dba    dbb     ------ ------ ------ ------     1 2    1 2   1 20   1 20    ------ ------ ------ ------   See the difference  We try to next example  SELECT fla flb  dba dbb FROM  test    Hola  We can find the difference like this   -------------------- ---------    fla flb              dba dbb    -------------------- ---------    2 4000000953674316      2 40    -------------------- ---------

User · Answer

Float has 32 bit  4 bytes  with 8 places accuracy  Double has 64 bit  8 bytes  with 16 places accuracy   If you need better accuracy  use Double instead of Float

User · Answer

They both represent floating point numbers  A FLOAT is for single-precision  while a DOUBLE is for double-precision numbers   MySQL uses four bytes for single-precision values and eight bytes for double-precision values   There is a big difference from floating point numbers and decimal  numeric  numbers  which you can use with the DECIMAL data type  This is used to store exact numeric data values  unlike floating point numbers  where it is important to preserve exact precision  for example with monetary data

[mysql] MySQL: What's the difference between float and double?

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