As stated earlier, the CASE statement is a conditional expression, so it can be used with any statement or clause where an expression can be used, such as a WHERE clause, SELECT statement, etc. Postgres supports two forms of the CASE statement: A Searched CASE and a Simple CASE. Basic S...
select to_char(now(),'yyyy-mm-dd hh24:mi:ss') "巡检时间", current_database() AS db, schemaname, tablename,bs, reltuples::bigint AS tups, relpages::bigint AS pages, otta, ROUND(CASE WHEN otta=0 OR sml.relpages=0 OR sml.relpages=otta THEN 0.0 ELSE sml.relpages/otta::numer...
也就是说其他尝试UPDATE、DELETE、SELECT FOR UPDATE、SELECT FOR NO KEY UPDATE、SELECT FOR SHARE或者SELECT FOR KEY SHARE这些行的事务将被阻塞,直到当前事务结束。 反过来,SELECT FOR UPDATE 将等待已经在相同行上运行以上这些命令的并发事务,并且接着锁定并且返回被更新的行(或者没有行,因为行可能已被删除)。 F...
LOG: duration: 5203.752 ms statement: insert into tab_test select i from generate_series(1,1000000)i; pg_stat_statements 插件监控 PostgreSQL 提供了 pg_stat_statements 插件用于追踪一个实例执行的所有 SQL 语句的统计信息。这个插件更详细的介绍可以参考PostgreSQL pg_stat_statements 插件文档。 如果要对数...
SELECT FOR UPDATE和SELECT FOR SHARE命令在目标表上会获得一个这种模式的锁。(加上在被引用但没有选择FOR UPDATE/FOR SHARE的任何其他表上的 ACCESS SHARE 锁。) ROW EXCLUSIVE 行独占 UPDATE、DELETE和INSERT命令在目标表上会获得一个这种模式的锁。(加上在任何其他被引用表上的 ACCESS SHARE锁。)通常,这种锁模...
Statement3.. ENF IF; 1. 2. 3. 4. 5. 6. 7. 8. case when --每个when条件只会执行一次,一旦匹配到true条件,后续不在执行 case selector when condition1 then statement1 when condition2 then statement2 else statementn end case; --搜索式: ...
Besides the WHERE clause, you can use other clauses in the SELECT statement for the SELECT INTO statement such as INNER JOIN, LEFT JOIN, GROUP BY, and HAVING. Note that you cannot use the SELECT INTO statement in PL/pgSQL because it interprets the INTO clause differently. In this case,...
标签PostgreSQL , adhoc查询 , 大宽表 , 任意字段组合查询 , 索引 , btree , gin , rum背景大宽表,任意字段组合查询,透视。是实时分析系统中的常见需求:1、实时写入。
ERROR: relation "sbtest$1" does not exist LINE 1: SELECT pad FROM "sbtest$1" WHERE id = $2; ^ client 0 aborted in state 1: ERROR: prepared statement "P0_1" does not exist ERROR: relation "sbtest$1" does not exist LINE 1: SELECT pad FROM "sbtest$1" WHERE id = $2; ^ ...
SELECT FOR SHARE语句在关系locktest上创建一个“RowShareLock”锁。 下面是用SQL语句创建的完全相同的锁: 00 BEGIN;LOCK TABLE locktest IN ROW SHARE MODE; 不管查询锁定的行数是多少,都需要一个重量级的RowShareLock。 在下面的示例中,用一个未完成的事务来说明这一点。启动未完成的事务,在第二个数据库连接...