SQL(Structured Query Language)是与数据库交互的主要语言,无论是数据检索、插入、更新还是删除操作都离不开 SQL 查询。掌握基本的 SQL 查询语法后,深入理解并应用高级查询技巧可以显著提高数据处理效率和查询性能。本篇文章将介绍几种常用的 SQL 高级查询技巧,帮助你在实际工作中提升查询效率和数据处理能力。 窗口函数...
其中Query中需要重点注意的是rtable,jointree,targetlist,分别表示查询的范围表,连接关系,需要投影的列 展示 在print.h给出了elog_node_display用于在源代码中调用来打印查询树,从而进行分析. 另外官方提供的runtime-config-logging也有很多参数来控制查询树的打印. debug_pretty_print 以结构化方式打印 debug_print_p...
表和视图有View, Edit, Rename, Drop, Query data 和Edit data等功能。 View和Edit分别是查看和修改表的结构信息,如字段,主键,索引和约束等。 Query data相当于新打开一个窗口,并执行select * from 表。 Edit data相当于新打开一个窗口,并执行select * from 表 for update。 存储过程和函数有Test功能,选中后...
The termtable wildcard functionrefers to a special type of function unique to Query. These functions are used in theFROMclause to match a collection of table names using one of several types of filters. For example, theTABLE_DATE_RANGEfunction can be used to query only a specific set of d...
[i].StrLen_or_Ind)); // all catalogs query printf( "A list of names of all catalogs\n" ); retCode = SQLTables( hstmt, (SQLCHAR*)SQL_ALL_CATALOGS, SQL_NTS, (SQLCHAR*)"", SQL_NTS, (SQLCHAR*)"", SQL_NTS, (SQLCHAR*)"", SQL_NTS ); for ( retCode = SQLFetch(...
SQLQuery<T> addSynchronizedQuerySpace(String querySpace) Deprecated. Adds a query space. List<NativeSQLQueryReturn> getQueryReturns() Deprecated. Retrieve the returns associated with this query. boolean isCallable() Deprecated. Is this native-SQL query known to be callable? NativeQuery<T> set...
XQuery Functions on String Values Functions on Boolean Values Functions on Nodes Context Functions Functions on Sequences Aggregate Functions (XQuery) Data Accessor Functions Constructor Functions (XQuery) Boolean Constructor Functions (XQuery) Functions Related to QNames (XQuery) ...
For more information, see Data Returned by Catalog Functions.Expand table Column nameColumn numberData typeComments TABLE_CAT (ODBC 1.0) 1 Varchar Catalog name of the table to which the statistic or index applies; NULL if not applicable to the data source. If a driver supports catalogs for ...
If a driver supportsSQLConnect, the driver keyword section of the system information for the driver must contain theConnectFunctionskeyword with the first character set to "Y." Connection Pooling Connection pooling allows an application to reuse a connection that has already been created. When connec...
Binary Functions:https://prestodb.io/docs/current/functions/binary.html from_utf8(binary) → varchar# Decodes a UTF-8 encoded string from binary. Invalid UTF-8 sequences are replaced with the Unicode replacement character U+FFFD. from_base64(string) → varbinary# ...