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REAL ​

REAL and FLOAT are floating-point data types. These data types store numeric values with variable precision. Some values may be stored as approximations; you may see slight discrepancies between a value that is loaded and value that is returned. The DECIMAL data type provides more exact results.

The REAL data type stores 32-bit floating-point values (4 bytes). The precision of a REAL column is 6 digits.

FLOAT4 is a valid synonym for REAL.

Note: FLOAT4 and FLOAT(4) are not synonyms. Yellowbrick permits the float(p) syntax but will promote it to the next floating-point number into which it will fit. This behavior is different than PostgreSQL.

Leading zeroes and whitespace characters are allowed. Trailing whitespace characters are also allowed.

Note: Yellowbrick supports NaN (not a number) and Infinity as floating-point values. The system can store and operate on these values.

  • Conversion of NaN, Infinity, +inf, and -inf to string types produces the appropriate string.
  • DECIMAL and INTEGER types do not support these values for storage or conversion.
  • When NaN is compared to a number, the result of the comparison is always false.
  • When an ORDER BY clause sorts NaN with numbers, NaN always sorts as greater than those numbers.

The following example demonstrates the values that you can load into a REAL column. Note that floating-point values with excess digits on the right side of the decimal point are rounded. Values with excess digits on the left side of the decimal point are converted to scientific notation; these values are not rejected.

premdb=# create table realtest(c1 real);
CREATE TABLE
premdb=# \d realtest
  Table "public.realtest"
 Column | Type | Modifiers 
--------+------+-----------
 c1     | real | 

Distribution: Hash (c1)

premdb=# insert into realtest values(100.1238);
INSERT 0 1
premdb=# select * from realtest;
   c1    
---------
 100.124
(1 row)

premdb=# insert into realtest values(100000);
INSERT 0 1
premdb=# select * from realtest;
   c1    
---------
 100.124
  100000
(2 rows)

premdb=# insert into realtest values(1000000);
INSERT 0 1
premdb=# select * from realtest;
   c1    
---------
 100.124
  100000
   1e+06
(3 rows)

You can insert Nan and Infinity values into a REAL or DOUBLE PRECISION column (and convert them to character strings):

premdb=# insert into realtest values('-inf');
INSERT 0 1
premdb=# insert into realtest values('+inf');
INSERT 0 1
premdb=# insert into realtest values('NaN');
INSERT 0 1
premdb=# select * from realtest order by c1;
   c1     
-----------
 -Infinity
   100.124
   100000
    1e+06
  Infinity
      NaN
(6 rows)

premdb=# select c1::varchar from realtest order by c1;
   c1     
-----------
 -Infinity
 100.124
 100000
 1e+06
 Infinity
 NaN
(6 rows)

Parent topic:SQL Data Types