String operands

Strings are sequences of any printable characters. Strings are always enclosed in double-quotes. Some examples are:

"This is a string"

"sinusoid"

"14-Dec-97"

Note: Character strings might look like tagnames or time expressions, as in the second and third examples above. In some cases, the string in the third example might be interpreted as a time. The difference is that a character string is enclosed in double quotes (for example, "string") while a tagname must be enclosed in single quotes (for example, 'tagname') and a time expression may be enclosed in either single or double quotes.