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3 | 3 | <appendix id="sql-keywords-appendix"> |
4 | 4 | <title><acronym>SQL</acronym> Key Words</title> |
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17 | 17 |
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18 | 18 | <para> |
19 | 19 | SQL distinguishes between <firstterm>reserved</firstterm> and |
20 | | - <firstterm>non-reserved</firstterm> key words. Reserved key words |
| 20 | + <firstterm>non-reserved</firstterm> key words. According to the standard, |
| 21 | + reserved key words |
21 | 22 | are the only real key words; they are never allowed as identifiers. |
22 | 23 | Non-reserved key words only have a special meaning in particular |
23 | 24 | contexts and can be used as identifiers in other contexts. Most |
24 | 25 | non-reserved key words are actually the names of built-in tables |
25 | | - and functions specified by SQL and the concept of non-reserved key |
| 26 | + and functions specified by SQL. The concept of non-reserved key |
26 | 27 | words essentially only exists to declare that some predefined meaning |
27 | 28 | is attached to a word in some contexts. |
28 | 29 | </para> |
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33 | 34 | ranging from those that can never be used as an identifier to those |
34 | 35 | that have absolutely no special status in the parser as compared to |
35 | 36 | an ordinary identifier. (The latter is usually the case for |
36 | | - functions specified by SQL.)SQL reserved key words are not |
| 37 | + functions specified by SQL.)Even reserved key words are not |
37 | 38 | completely reserved in <productname>PostgreSQL</productname>, but |
38 | | - can be used as columnlabel (as in <literal>SELECT 55 AS |
| 39 | + can be used as columnlabels (for example, <literal>SELECT 55 AS |
39 | 40 | CHECK</literal>, even though <token>CHECK</token> is a reserved key |
40 | 41 | word). |
41 | 42 | </para> |
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47 | 48 | known to the parser but are allowed in most or all contexts where an |
48 | 49 | identifier is expected. Some key words that are otherwise |
49 | 50 | non-reserved cannot be used as function or data type names and are |
50 | | - marked accordingly. (Some of thesetokens represent built-in |
| 51 | + marked accordingly. (Most of thesewords represent built-in |
51 | 52 | functions or data types with special syntax. The function or type |
52 | 53 | is still available but it cannot be redefined by the user.) Labeled |
53 | 54 | <quote>reserved</quote> are those tokens that are only allowed as |
54 | 55 | <quote>AS</quote> column label names (and perhaps in very few other |
55 | | - contexts). Some reserved key words areavailable as names for |
| 56 | + contexts). Some reserved key words areallowable as names for |
56 | 57 | functions; this is also shown in the table. |
57 | 58 | </para> |
58 | 59 |
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