5. Sorting, Grouping and Compound SELECTs When values are sorted by an ORDER by clause, values with storage class NULL come first, followed by INTEGER and REAL values interspersed in numeric order, followed by TEXT values usually in memcmp() order, and finally BLOB values in memcmp() order....
in which case the specified collating function is used for sorting. Otherwise, if the expression sorted by an ORDER BY clause is a column, then the collating sequence of the column is used to determine sort order. If the expression is not a column ...
另一种是 OR 连接的,这需要两部分查询结果通过 UNION; 处理ORDER BY 的时候往往可以利用 INDEX 提高速度,因为没有 INDEX 的时候需要将无序的结果 online sorting,而如果排序域存在 INDEX,就可以直接利用这个顺序遍历; covering index 的存在可以解决 filtering field 和 sorting field 同时存在的时候的性能。 ——...
*/SELECTcount(*)FROMt1GROUPBY(d||'')ORDERBY1;--结果 1 1 2/* 列c排序表现为使用 RTRIM 整理序列。*/(译注:sortingorcolumnc 疑为 sorting of...误写)SELECTxFROMt1ORDERBYc, x;--结果 4 1 2 3/* (c||'')排序表现为使用 BINARY 整理序列。*/SELECTxFROMt1ORDERBY(c||''), x;--结果 ...
u16 wctrlFlags/*One of the WHERE_* flags defined in sqliteInt.h*/ ) pTabList是由分析器对FROM部分生成的语法树,它包含FROM中表的信息;pWhere是WHERE部分的语法树,它包含WHERE中所有表达式的信息;ppOrderBy 对应ORDER BY子句(暂不考虑)。 Sqlite的查询优化做得简单又精致。在一个简单的sqlite3WhereBegin...
SELECT count(*) FROM t1 GROUP BY (d || '') ORDER BY 1; --result 1 1 2 /* Sorting or column c is performed using the RTRIM collating sequence. */ SELECT x FROM t1 ORDER BY c, x; --result 4 1 2 3 /* Sorting of (c||'') is performed using the BINARY collating sequence....
ORDER BY first_name DESC; Example - Using both ASC and DESC attributes When sorting your result set using the SQLite ORDER BY clause, you can combine the ASC and DESC attributes in a singleSELECT statement. For example: SELECT employee_id, last_name, first_name ...
"Sorting And Searching", pages 473-480. Addison-WesleyPublishing Company, Reading, Massachusetts. ** 基本思想是文件包含的每一页都包括N个数据库入口和N+1个指向子页的指针。文件分成很多页存储。为什么这么干,因为内存分页管理机制闹得。外存中每个页就是B树的一个节点。
-- Sorting is performed using the BINARY collation sequence. SELECT * FROM t1 ORDER BY (c || ''); -- Sorting is performed using the NOCASE collation sequence. SELECT * FROM t1 ORDER BY c COLLATE NOCASE; 1. 2. 3. 4. 5.
explicit_ordering (bool)– Order using full SQL function to calculate rank, as opposed to simply referencing the score alias in the ORDER BY clause. Shorthand way of searching for a term and sorting results by the quality of the match using the BM25 algorithm. Attention The BM25 ranking algor...