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2 | 2 | Frequently Asked Questions (FAQ) for PostgreSQL |
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4 | | - Last updated: ThuApr 26 20:55:41 EDT 2001 |
| 4 | + Last updated: ThuMay 10 21:32:49 EDT 2001 |
5 | 5 |
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6 | 6 | Current maintainer: Bruce Momjian (pgman@candle.pha.pa.us) |
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74 | 74 | 4.11) What is an R-tree index? |
75 | 75 | 4.12) What is the Genetic Query Optimizer? |
76 | 76 | 4.13) How do I perform regular expression searches and |
77 | | - case-insensitive regular expression searches? |
| 77 | + case-insensitive regular expression searches? How do I use an index |
| 78 | + for case-insensitive searches? |
78 | 79 | 4.14) In a query, how do I detect if a field is NULL? |
79 | 80 | 4.15) What is the difference between the various character types? |
80 | 81 | 4.16.1) How do I create a serial/auto-incrementing field? |
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233 | 234 |
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234 | 235 | 1.7) What is the latest release? |
235 | 236 |
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236 | | - The latest release of PostgreSQL is version 7.1. |
| 237 | + The latest release of PostgreSQL is version 7.1.1. |
237 | 238 |
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238 | 239 | We plan to have major releases every four months. |
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@@ -751,12 +752,24 @@ Maximum number of indexes on a table? unlimited |
751 | 752 | join queries through nonexhaustive search. |
752 | 753 |
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753 | 754 | 4.13) How do I perform regular expression searches and case-insensitive |
754 | | - regular expression searches? |
| 755 | + regular expression searches? How do I use an index for case-insensitive |
| 756 | + searches? |
755 | 757 |
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756 | 758 | The ~ operator does regular expression matching, and ~* does |
757 | 759 | case-insensitive regular expression matching. The case-insensitive |
758 | 760 | variant of LIKE is called ILIKE in PostgreSQL 7.1 and later. |
759 | 761 |
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| 762 | + Case-insensitive equality comparisons are normally expressed as: |
| 763 | + SELECT * |
| 764 | + FROM tab |
| 765 | + WHERE lower(col) = 'abc' |
| 766 | + |
| 767 | + |
| 768 | + This will not use an standard index. However, if you create a |
| 769 | + functional index, it will be used: |
| 770 | + CREATE INDEX tabindex on tab (lower(col)); |
| 771 | + |
| 772 | + |
760 | 773 | 4.14) In a query, how do I detect if a field is NULL? |
761 | 774 |
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762 | 775 | You test the column with IS NULLIS NOT NULL. |
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