caohong286的专栏

Chapter3  Access and Join Methods 访问和连接方法Karen Morton     (page 83)    The optimizer must determine how to access the data your SQL statements require. You formulate your statement and the opt...

Cartesian Joins     笛卡尔连接     (page 118)    Cartesian joins occur when all the rows from one table are joined to all the rows of another table.  Therefore, the total number of rows resulting fro...

Hash Joins    哈希连接      (page 116)     Hash joins, like sort-merge joins, first reads the two tables to be joined independently and applies the criteria in the WHERE clause.  Based on table an...

Sort-Merge Joins    排序-合并连接      (page 114)   Sort-merge joins read the two tables to be joined independently, sorts the rows from each table (but only those rows that meet the conditions for th...

Nested Loops Joins  嵌套循环连接       (page 111)    Nested loops joins use each row of the query result reached through one access operation to drive into another table.  These joins are typically ...

Join Methods  连接方法  (page 110)    If there are multiple tables in your query, after the optimizer determines the access methods most appropriate for each of the tables, the next step is to det...

Index Fast Full Scan  索引快速全扫描   (page 109)    An index fast full scan is more like a full table scan than like other index scan types.  When an index fast full scan operation is chosen, all th...

Index Skip Scan    索引跳跃扫描    (page 107)    An index skip scan is chosen when the predicate contains a condition on a non-leading column in an index and the leading columns are fairly disti...

Index Full Scan  索引全扫描  (page 103)    An index full scan is chosen under several conditions including: when there is no predicate but the column list can be satisfied through an index on a col...

Index range scan    索引范围扫描   (page 101)    An index range scan is chosen when a predicate contains a condition that will return a range of data.  The index can be unique or non-unique as it ...

Index Unique Scan    索引唯一扫描    (page 78)    An index unique scan is chosen when a predicate contains a condition using a column defined with a UNIQUE or  PRIMARY KEY  index.  These types of in...

Index Scan Types  索引扫描类型     (page 97)    There are several different types of index scans but each share some common ground in how they must traverse the index structure to access the leaf bloc...

Index Scan Access Methods      索引扫描访问方法  (page 95)    If you have a book about U.S. Presidents and want to find information on Jimmy Carter, you could start on the first page and visually ...

Full Scans and the Highwater Mark    全扫描和高水标识    A final point of note regarding full table scans is that as the multiblock read calls for the scan are made, Oracle will read blocks up to the ...

Full Scans and Throwaway  全扫描和“抛弃”    Always remember that whether or not a full scan will be an effective choice depends on the number of blocks that will need to be read as much as on how ma...

Outer Joins    外连接     (page 120)     An outer join returns all rows from one table and only those rows from the joined table where the join condition is met.  Oracle uses the  + character...