You use SQL value expressions to combine two or more values. Several kinds of SQL value expressions exist, corresponding to the different data types; the following tables list string, numeric, and datetime values, functions, and effects:
String Value Functions
| Function |
Effect |
| SUBSTRING |
Extracts a substring from a source string |
| UPPER |
Converts a character string to all uppercase |
| LOWER |
Converts a character string to all lowercase |
| TRIM |
Trims off leading or trailing blanks |
| TRANSLATE |
Transforms a source string from one character set to
another |
| CONVERT |
Same as TRANSLATE. (It transforms a source string from one
character set to another.) |
Numeric Value Functions
| Function |
Effect |
| POSITION |
Returns the starting position of a target string within a
source string |
| CHARACTER_LENGTH |
Returns the number of characters in a string |
| OCTET_LENGTH |
Returns the number of octets (bytes) in a character string |
| EXTRACT |
Extracts a single field from a datetime or interval |
Datetime Value Functions
| Function |
Effect |
| CURRENT_DATE |
Returns the current date |
| CURRENT_TIME(p) |
Returns the current time; (p) is precision of seconds |
| CURRENT_TIMESTAMP(p) |
Returns the current date and the current time; (p) is precision
of seconds |
