Difference between revisions of "Portable SQL/Common/Aliases"
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(→Alias for tables and columns) |
(aliasing columns and computed columns) |
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| − | = | + | = Using aliases = |
| − | Don't use the keyword "AS" between name and alias as no DBMS requires it and some don't recognize it. Instead, always write | + | == Aliasing tables == |
| + | |||
| + | Don't use the keyword "AS" between the table name and alias as no DBMS requires it and some don't recognize it. Instead, always write: | ||
SELECT * FROM table t WHERE t.id = 0 | SELECT * FROM table t WHERE t.id = 0 | ||
| + | |||
| + | == Aliasing columns == | ||
| + | |||
| + | Contrary to "Aliasing tables" the keyword "AS" between column name and alias is required by most database servers and should always be present: | ||
| + | |||
| + | SELECT count(*) AS cnt FROM table | ||
| + | |||
| + | == Aliases for computed columns == | ||
| + | |||
| + | The naming of computed columns implemented by the database servers is very different. Some name it like the computational expression ('count(*)'), most often in upper case and sometimes it isn't named at all. Therefore computed columns should be always given a name: | ||
| + | |||
| + | SELECT MAX(id) AS maxid FROM table | ||
---- | ---- | ||
Back to [[OpenDBX|Overview]] | Back to [[OpenDBX|Overview]] | ||
Revision as of 16:19, 10 March 2007
Using aliases
Aliasing tables
Don't use the keyword "AS" between the table name and alias as no DBMS requires it and some don't recognize it. Instead, always write:
SELECT * FROM table t WHERE t.id = 0
Aliasing columns
Contrary to "Aliasing tables" the keyword "AS" between column name and alias is required by most database servers and should always be present:
SELECT count(*) AS cnt FROM table
Aliases for computed columns
The naming of computed columns implemented by the database servers is very different. Some name it like the computational expression ('count(*)'), most often in upper case and sometimes it isn't named at all. Therefore computed columns should be always given a name:
SELECT MAX(id) AS maxid FROM table
Back to Overview
