# Built-in Functions → Boolean Functions

## Finding Strings Within Strings

These functions find a substring within a given string. They return true if the substring is found and false otherwise. In the table, field is the string to search. It is an expression evaluating to a `string` type. The string to search for is find.

FunctionSignatureDescription
startsWith()`startsWith(field exp, find1, find2, ...)`Determine whether a string starts with a substring(s)
contains()`contains(field exp, find1, find2, ...)`Determine whether a string contains a given substring(s)
endsWith()`endsWith(string expr field, string find)`Determine whether a string ends with a given substring
like()`like(string expr field, string expr pattern, string esc)`Returns true if pattern is found within field
isAlpha()`isAlpha(value)`Determine whether a string consists of alphabetic characters only
isNumeric()`isNumeric(value)`Determine whether a string evaluates as a number

## Comparing Expressions with Constants

These functions find a constant (constN) in an expression (field). If one of the constants is found in field, true is returned. These functions return false otherwise.

FunctionSignatureDescription
in`in(expr field, const1, const2, ...)`Return true if any of a list of items match the given expression
inList`inList(expr field, list)`Return true if an expression evaluates to one or more constants in list

## Find NULLs and NaNs

These functions check whether values can be used in further operations.

FunctionSignatureDescription
isNull()`isNull(<type> expr field )`Returns true if field evaluates to NULL
isNan()`isNan(double value)`Returns true if value is NaN

## Compare Booleans

These functions operate on expressions evaluating to `boolean`. They are the logical functions Incorta supports.

FunctionSignatureDescription
and()`and(bool expr1, bool expr2, . . .)`Determine whether a series of expressions evaluate to true
or()`or(bool expr1, bool expr2, . . .)`Determines whether any of a series of expressions evaluate to true
not()`not(bool expr)`Negates its expression argument

## Checking Ranges

FunctionSignatureDescription
between()`between(double expr value, double expr min, double expr max)`Returns true if value is between min and max