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Dây phải được kèm theo một trong hai dấu nháy đơn hoặc kép. Dưới đây là một chuỗi: "Tôi trái tim của tôi ở San Francisco", "$ 19,95" Bạn có thể đặt "văn bản trích dẫn" trong một chuỗi. '' Bạn thậm chí có thể bao gồm một dấu nháy đơn trong văn bản của một string' " | 174 Part III Advanced Report Types and Features Strings must be enclosed in either single or double quotes. Here are a few strings I Left My Heart in San Francisco 19.95 You can put quoted text within a string. You can even include an apostrophe in a string s text As you can see sometimes you must use quotes in an unusual way to keep from confusing the string parser. The string parser is the part of Crystal Reports that analyzes and interprets strings one character at a time. Anything within quotes is a string even if it looks like a number or a currency value. Date time and datetime As you might surmise the date data type holds dates the time data type holds times and datetime data type holds a combination of the date and time. Date and time data types are somewhat redundant because the datetime data type can hold dates without times and times without dates. You might want to use the date or the time data type anyway though because data in those two types takes up less storage space in memory and on the hard disk than the same quantity stored as a datetime data type. Datetime values are not strings or numbers. They are literals which are handled differently from the way either strings or numbers are handled. Datetime literals are enclosed in pound signs. This differentiates them from strings which are quoted and numbers which are not enclosed in anything . Following are some examples of values that can be stored in the datetime data type July 20 1969 20 Jul 1969 4 18 pm 7 20 1969 16 18 00 7 20 1969 4 18 pm Boolean Boolean data is named after the British mathematician George Boole who invented Boolean algebra which gave logic a mathematical foundation. Boolean data has only two values True and False. Crystal Reports accepts Yes and No as synonyms for True and False. Boolean logic has been critical to the development of the digital computer which uses ones and zeros to represent True and False. Chapter 11 Adding Formulas to Reports 175 Range data types Crystal .
