ABAP CDS-基础语法规则

The general syntax rules for the DDL and the DCL in ABAP CDS are:

• Keywords

• Keywords must be all uppercase, all lowercase, or in lowercase with an uppercase initial letter. Mixed uppercase and lowercase is not allowed.

• Names

• Names are not case-sensitive.

• A name can have a maximum of 30 characters.

• A name can consist of letters, numbers, underscores (_), and slashes (/).

• A name must start with a letter or a forward slash character.

• The following CDS keywords cannot be used in names: ALL, AND, AS, ASSOCIATION, AVG, CASE, CAST, COUNT, DISTINCT, EXISTS, EXTEND, FROM, FULL, GROUP, HAVING, INNER, JOIN, KEY, LEFT, MAX, MIN, NOT, NULL, ON, OR, ORDER, RIGHT, SELECT, SUM, UNION, VIEW, WHEN, WHERE

• Literals

• Numeric literals must always be specified in full and a decimal point (.) used as a decimal separator if necessary.

• Character literals are enclosed in single quotations marks (').

• Comments

• Two forward slashes (//) introduce a comment, which continues until the end of the line.

• Comments within lines or that span multiple lines are enclosed by the characters /* and */.

• Separators

• Statements can be closed using a semicolon (;). This is optional.

• Protected Words

• Certain keywords are protected and cannot be used as self-defined names.

Examples

• SELECT, select, and Select are valid ways are specifying a keyword. seLect and SeLect, on the other hand, produce syntax errors.

• MYVIEW, myview, and myView all identify the same operand.

• 0.5 is a valid numeric literal, but .5 is not.