PLpgSQL is the preferred language, except for "pure SQL".
#Postgresql round code#
The IMMUTABLE clause is very important for code snippets like this, because, as said in the Guide: "allows the optimizer to pre-evaluate the function when a query calls it with constant arguments" Two precautions must be taken when implementing user-defined cast functions for high performance: The build-in functions, such as ROUND of the pg_catalog, can be overloaded with no performance loss, when compared to direct cast encoding. There are a lack of overloads in some PostgreSQL functions, why (?): I think "it is a lack" (!), but and the PostgreSQL team agree about "pg's historic rationale". The to_char function apply internally the round procedure, so, when your aim is only to show a final result in the terminal, you can use the FM modifier as a prefix to a numeric format pattern: SELECT round(x::numeric,2), trunc(x::numeric,2), to_char(x, 'FM99.99')
The pg_catalog functions are the default ones, see at Guide the build-in math functions. Where float is synonymous of double precision and myschema is public when you not use a schema. Pg_catalog | round | numeric | numeric, int PS: the command \df round, on psql after overloadings, will show something like this table Other alternative, overloading ROUND function again, and using all range of accuracy-precision of a floating point number, is to return a float when the accuracy is defined (see IanKenney's answer), CREATE FUNCTION ROUND(Īccuracy float - accuracy, the "counting unit" An alternative is to use round(f,3)::float or to create a round_tofloat() function. In another applications we need a float also as result. The ROUND(float,int) function is f_round, it returns a (decimal) NUMERIC datatype, that is fine for some applications: problem solved! The FM prefix tells to_char that you don't want any padding with leading spaces. To_char will round numbers for you as part of formatting. Use to_char (see: data type formatting functions in the manual), which lets you specify a format and gives you a text result that isn't affected by whatever weirdness your client language might do with numeric values. If you're formatting for display to the user, don't use round. Just append ::numeric for the shorthand cast, like round(val::numeric,2). You must cast the value to be rounded to numeric to use the two-argument form of round. You can see that PostgreSQL is expanding it in the output). (In the above, note that float8 is just a shorthand alias for double precision. Regress=> SELECT round( CAST(float8 '3.1415927' as numeric), 2)
Pg_catalog | round | numeric | numeric, integer | normal Pg_catalog | round | numeric | numeric | normal Pg_catalog | round | double precision | double precision | normal Pg_catalog | dround | double precision | double precision | normal Schema | Name | Result data type | Argument data types | Type regress=> SELECT round( float8 '3.1415927', 2 ) ĮRROR: function round(double precision, integer) does not exist For reasons Sherrill 'Cat Recall' explains in the comments, the version of round that takes a precision is only available for numeric. WITH RECURSIVE summary_stats AS ( SELECT ROUND( AVG(duration_minutes), 2) AS mean, PERCENTILE_CONT(0.5) WITHIN GROUP ( ORDER BY duration_minutes) AS median, MIN(duration_minutes) AS min, MAX(duration_minutes) AS max, MAX(duration_minutes) - MIN(duration_minutes) AS range, ROUND( STDDEV(duration_minutes), 2) AS standard_deviation, ROUND( VARIANCE(duration_minutes), 2) AS variance, PERCENTILE_CONT(0.25) WITHIN GROUP ( ORDER BY duration_minutes) AS q1, PERCENTILE_CONT(0.PostgreSQL does not define round(double precision, integer). In the below query, we’ll create two CTEs namely summary_stats (which returns the previously discussed statistics one per each column) and row_summary_stats (which returns the statistics one per each row). We’ll put all the functions discussed earlier together and return them in a single table.
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