select语句中的PostgreSQL - if子句 PostgreSQL是一种开源的关系型数据库管理系统(RDBMS),它支持广泛的SQL语言特性和功能。在PostgreSQL中,if子句是一种条件语句,用于根据特定条件执行不同的操作。 if子句的语法如下: 代码语言:txt 复制 IF condition THEN statements; ELSE statements; END IF; 其中,condition是一个...
SELECTselect_expressionsINTO[STRICT]targetFROM...;INSERT...RETURNINGexpressionsINTO[STRICT]target;UPDATE...RETURNINGexpressionsINTO[STRICT]target;DELETE...RETURNINGexpressionsINTO[STRICT]target; 举个例子,如下: 代码语言:javascript 复制 --这就表示把test表中的id字段的值赋值给a--其中 select id from test就...
IF 语句 IF 语句可以基于条件选择性执行操作, PL/pgSQL 提供了三种形式的 IF 语句。 IF ... THEN ... END IF IF ... THEN ... ELSE ... END IF IF ... THEN ... ELSIF ... THEN ... ELSE ... END IF 首先,最简单的 IF 语句如下: IF boolean-expression THEN statements END IF; 如果...
the if statement doesn’t handle the false condition. To handle the false conditions, theelse statementis used in PostgreSQL. Therefore, the statements/commands affiliated with the if statement will execute only if the given condition/expression is true. However, the statements specified ...
#ifdefined(CX) int cycle_diffs =0; int mutations =0; #endif/* 配置私有信息;set up private information */root->join_search_private = (void *) &private; private.initial_rels = initial_rels;/* 初始化种子值;initialize private number generator */geqo_set_seed(root, Geqo_seed);/* 设置遗...
A SELECT INTO statement sets FOUND true if a row is assigned, false if no row is returned. A PERFORM statement sets FOUND true if it produces (and discards) one or more rows, false if no row is produced. UPDATE, INSERT, and DELETE statements set FOUND true if at least one row is ...
定位一个游标。 MOVE [ direction { FROM | IN } ] cursor_nameNOTIFY生成一个通知。NOTIFY namePREPARE创建一个准备好的查询。PREPARE plan_name [ (data_type [, ...] ) ] AS statementREINDEX重建索引。REINDEX { DATABASE | TABLE | INDEX } name [ FORCE ]...
PostgreSQL可以不借助任何扩展实现对SQL日志的记录,主要依赖于两个参数,也即log_statement和log_min_duration_statement, 1,记录的sql类型 log_statement='all' 可以是none, ddl, mod, all 2,记录的sql执行时间阈值 log_min_duration_statement='1000',单位毫秒,记录超出该单位时间的log_statement中定义类型的SQL ...
SELECT SEQUENCE SEQUENCES SERIALIZABLE SERVER SESSION SESSION_USER SET SETS SETOF SHARE SHOW SIMILAR SIMPLE SKIP SMALLINT SNAPSHOT SOME SQL_P STABLE STANDALONE_P START STATEMENT STATISTICS STDIN STDOUT STORAGE STRICT_P STRIP_P SUBSCRIPTION SUBSTRING SYMMETRIC SYSID SYSTEM_P TABLE TABLES TABLESAMPLE ...
MyTest=# SELECT set_config('log_statement_stats','off', false); set_config --- off (1 row) 2. 数据库对象尺寸函数: 名字 返回类型 描述 pg_tablespace_size(oid) bigint 指定OID代表的表空间使用的磁盘空间 pg_tablespace_size(name) bigint 指定名字的表空间使用的磁盘空间 pg_database_size(oid...