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Overview
| Comment: | Additional cleanup in the SQL language documentation. |
|---|---|
| Timelines: | family | ancestors | descendants | both | trunk |
| Files: | files | file ages | folders |
| SHA1: |
d508b9e21cd6cd2b22f571f00906c5cb |
| User & Date: | drh 2009-12-13 23:03:41 |
Context
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2009-12-14
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| 17:41 | For the requirements matrix, scan evidence marks in the original source code, not in the amalgamation. Updates to SQL comment documentation. check-in: dca51f132e user: drh tags: trunk | |
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2009-12-13
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| 23:03 | Additional cleanup in the SQL language documentation. check-in: d508b9e21c user: drh tags: trunk | |
| 22:20 | Updates to the SQL language documentation - mostly to fix requirements marks. check-in: b80a69c002 user: drh tags: trunk | |
Changes
Changes to pages/lang.in.
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<p>^The LIKE operator does a pattern matching comparison. ^The operand to the right of the LIKE operator contains the pattern and the left hand operand contains the string to match against the pattern. <tcl>hd_puts "^A percent symbol (\"%\") in the LIKE pattern matches any sequence of zero or more characters in the string. ^An underscore (\"_\") in the LIKE pattern matches any single character in the string. ^(Any other character matches itself or it's lower/upper case equivalent (i.e. case-insensitive matching).)^ (A bug: ^SQLite only understands upper/lower case for ASCII characters by default. ^The LIKE operator is case sensitive by default for unicode characters that are beyond the ASCII range. For example, ^the expression <b>'a' LIKE 'A'</b> is TRUE but <b>'æ' LIKE 'Æ'</b> is FALSE.)<p>"</tcl> ................................................................................ application-defined function. ^The default match() function implementation raises an exception and is not really useful for anything. ^But extensions can override the match() function with more helpful logic.</p> <tcl>hd_fragment between BETWEEN</tcl> <h3>The BETWEEN operator</h3> <p>^(The BETWEEN operator is equivalent to a pair of comparisons. "<i>a</i> <b>BETWEEN</b> <i>b</i> <b>AND</b> <i>c</i>" is equivalent to "<i>a</i><b>>=</b><i>b</i> <b>AND</b> <i>a</i><b><=</b><i>c</i>".)^ ^The precedence of the BETWEEN operator is the same as the precedence as operators <b>==</b> and <b>!=</b> and <b>LIKE</b> and groups left to right. <tcl>hd_fragment case {CASE expression}</tcl> <h3>The CASE expression</h3> <p>A CASE expression serves a role similar to IF-THEN-ELSE in other programming languages. ^WHEN expressions are evaluated from left to ................................................................................ arbitrary. } funcdef {max(X)} {*maxAggFunc *agg_max {max() aggregate function}} { ^The max() aggregate function returns the maximum value of all values in the group. ^The maximum value is the value that would be returned last in an ORDER BY on the same column. ^NULL is returned if and only if there are no non-NULL values in the group. } funcdef {min(X)} {*minAggFunc *agg_min {min() aggregate function}} { ^The min() aggregate function returns the minimum non-NULL value of all values in the group. ^The minimum value is the first non-NULL value that would appear in an ORDER BY of the column. ^NULL is returned if and only if there are no non-NULL values in the group. } funcdef {sum(X) total(X)} { *sumFunc *sum *total {sum() aggregate function} {total() aggregate function} } { ................................................................................ <h3>Restrictions on UPDATE Statements Within CREATE TRIGGER</h3> <p>^There are additional syntax restrictions on UPDATE statements that occur within the body of a [CREATE TRIGGER] statement. ^The <i>table-name</i> of the UPDATE must be unqualified. ^(In other words, the <i>database-name</i><b>.</b> prefix on the table name of the UPDATE is not allowed within triggers. ^The table to be updated must be in the same database as the table to which the trigger is attached.</p> <p>^The INDEXED BY and NOT INDEXED clauses are not allowed on UPDATE statements within triggers.</p> <p>^The LIMIT clause for UPDATE is unsupported within triggers.</p> ................................................................................ <p>^VACUUM only works on the main database. It is not possible to VACUUM an attached database file.</p> <p>^The VACUUM command will fail if there is an active transaction. ^The VACUUM command is a no-op for in-memory databases.</p> <p>^As of SQLite version 3.1, an alternative to using the VACUUM command is auto-vacuum mode, enabled using the [auto_vacuum] pragma. ^When [auto_vacuum] is enabled for a database, large deletes cause the size of the database file to shrink. However, [auto_vacuum] also causes excess fragmentation of the database file. ^And [auto_vacuum] does not compact partially filled pages of the database as VACUUM does.</p> <p>^The [page_size] and/or [auto_vacuum] mode of a database can be changed ................................................................................ <p> <blockquote> <table> <tr> <td valign="top"><b>'keyword'</b></td><td width="20"></td> <td>^A keyword in single quotes is a string literal.</td></tr> <tr> <td valign="top"><b>"keyword"</b></td><td></td> <td>^A keyword in double-quotes is an identifier</td></tr> <tr> <td valign="top"><b>[keyword]</b></td><td></td> <td>^A keyword enclosed in square brackets is an identifier. This is not standard SQL. This quoting mechanism is used by MS Access and SQL Server and is included in SQLite for compatibility.</td></tr> |
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<p>^The LIKE operator does a pattern matching comparison. ^The operand to the right of the LIKE operator contains the pattern and the left hand operand contains the string to match against the pattern. <tcl>hd_puts "^A percent symbol (\"%\") in the LIKE pattern matches any sequence of zero or more characters in the string. ^An underscore (\"_\") in the LIKE pattern matches any single character in the string. ^(Any other character matches itself or its lower/upper case equivalent (i.e. case-insensitive matching).)^ (A bug: ^SQLite only understands upper/lower case for ASCII characters by default. ^The LIKE operator is case sensitive by default for unicode characters that are beyond the ASCII range. For example, ^the expression <b>'a' LIKE 'A'</b> is TRUE but <b>'æ' LIKE 'Æ'</b> is FALSE.)<p>"</tcl> ................................................................................ application-defined function. ^The default match() function implementation raises an exception and is not really useful for anything. ^But extensions can override the match() function with more helpful logic.</p> <tcl>hd_fragment between BETWEEN</tcl> <h3>The BETWEEN operator</h3> <p>^(The BETWEEN operator is logically equivalent to a pair of comparisons. "<i>x</i> <b>BETWEEN</b> <i>y</i> <b>AND</b> <i>z</i>" is equivalent to "<i>x</i><b>>=</b><i>y</i> <b>AND</b> <i>x</i><b><=</b><i>z</i>" except that with BETWEEN, the <i>x</i> expression is only evaluated once.)^ ^The precedence of the BETWEEN operator is the same as the precedence as operators <b>==</b> and <b>!=</b> and <b>LIKE</b> and groups left to right. <tcl>hd_fragment case {CASE expression}</tcl> <h3>The CASE expression</h3> <p>A CASE expression serves a role similar to IF-THEN-ELSE in other programming languages. ^WHEN expressions are evaluated from left to ................................................................................ arbitrary. } funcdef {max(X)} {*maxAggFunc *agg_max {max() aggregate function}} { ^The max() aggregate function returns the maximum value of all values in the group. ^The maximum value is the value that would be returned last in an ORDER BY on the same column. ^Aggregate max() returns NULL if and only if there are no non-NULL values in the group. } funcdef {min(X)} {*minAggFunc *agg_min {min() aggregate function}} { ^The min() aggregate function returns the minimum non-NULL value of all values in the group. ^The minimum value is the first non-NULL value that would appear in an ORDER BY of the column. ^Aggregate min() returns NULL if and only if there are no non-NULL values in the group. } funcdef {sum(X) total(X)} { *sumFunc *sum *total {sum() aggregate function} {total() aggregate function} } { ................................................................................ <h3>Restrictions on UPDATE Statements Within CREATE TRIGGER</h3> <p>^There are additional syntax restrictions on UPDATE statements that occur within the body of a [CREATE TRIGGER] statement. ^The <i>table-name</i> of the UPDATE must be unqualified. ^(In other words, the <i>database-name</i><b>.</b> prefix on the table name of the UPDATE is not allowed within triggers.)^ ^The table to be updated must be in the same database as the table to which the trigger is attached.</p> <p>^The INDEXED BY and NOT INDEXED clauses are not allowed on UPDATE statements within triggers.</p> <p>^The LIMIT clause for UPDATE is unsupported within triggers.</p> ................................................................................ <p>^VACUUM only works on the main database. It is not possible to VACUUM an attached database file.</p> <p>^The VACUUM command will fail if there is an active transaction. ^The VACUUM command is a no-op for in-memory databases.</p> <p>^(As of SQLite version 3.1, an alternative to using the VACUUM command is auto-vacuum mode, enabled using the [auto_vacuum] pragma.)^ ^When [auto_vacuum] is enabled for a database, large deletes cause the size of the database file to shrink. However, [auto_vacuum] also causes excess fragmentation of the database file. ^And [auto_vacuum] does not compact partially filled pages of the database as VACUUM does.</p> <p>^The [page_size] and/or [auto_vacuum] mode of a database can be changed ................................................................................ <p> <blockquote> <table> <tr> <td valign="top"><b>'keyword'</b></td><td width="20"></td> <td>^A keyword in single quotes is a string literal.</td></tr> <tr> <td valign="top"><b>"keyword"</b></td><td></td> <td>^A keyword in double-quotes is an identifier.</td></tr> <tr> <td valign="top"><b>[keyword]</b></td><td></td> <td>^A keyword enclosed in square brackets is an identifier. This is not standard SQL. This quoting mechanism is used by MS Access and SQL Server and is included in SQLite for compatibility.</td></tr> |