Values that are too large or too small will cause an error. The DOUBLE type typically has a range of around 1E-307 to 1E+308 with a precision of at least 15 digits. On most platforms, the REAL type has a range of at least 1E-37 to 1E+37 with a precision of at least 6 decimal digits.
Comparing two floating-point values for equality might not always work as expected. If you want to do complicated calculations with these types for anything important, especially if you rely on certain behavior in boundary cases (infinity, underflow), you should evaluate the implementation carefully. If you require exact storage and calculations (such as for monetary amounts), use the numeric type instead. Managing these errors and how they propagate through calculations is the subject of an entire branch of mathematics and computer science and will not be discussed here, except for the following points: Inexact means that some values cannot be converted exactly to the internal format and are stored as approximations, so that storing and retrieving a value might show slight discrepancies. Single precision floating-point number (4 bytes)ĭouble precision floating-point number (8 bytes) In practice, these types are usually implementations of IEEE Standard 754 for Binary Floating-Point Arithmetic (single and double precision, respectively), to the extent that the underlying processor, operating system, and compiler support it. The data types REAL and DOUBLE precision are inexact, variable-precision numeric types. It is therefore recommended to stick with a width of 18 or below, unless there is a good reason for why this is insufficient. In particular decimal values with a width above 19 are very slow, as arithmetic involving the INT128 type is much more expensive than operations involving the INT32 or INT64 types. Performance can be impacted by using too large decimals when not required. Internally, decimals are represented as integers depending on their specified width. 
The default WIDTH and SCALE is DECIMAL(18,3), if none are specified.
For example, the type DECIMAL(3,2) can fit the value 1.23, but cannot fit the value 12.3 or the value 1.234. The WIDTH field determines how many digits can be held, and the scale determines the amount of digits after the decimal point. When creating a value of type DECIMAL, the WIDTH and SCALE can be specified to define which size of decimal values can be held in the field. The data type DECIMAL(WIDTH,SCALE) represents an exact fixed-point decimal value. The BIGINT and HUGEINT types are designed to be used when the range of the integer type is insufficient. The SMALLINT type is generally only used if disk space is at a premium. The type integer is the common choice, as it offers the best balance between range, storage size, and performance. Attempts to store negative numbers or values outside of the allowed range will result in an error Name The types UTINYINT, USMALLINT, UINTEGER, UBIGINT store whole unsigned numbers. Attempts to store values outside of the allowed range will result in an error. The types TINYINT, SMALLINT, INTEGER, BIGINT and HUGEINT store whole numbers, that is, numbers without fractional components, of various ranges.
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