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select prod_name,prod_price from products where prod_price = 2.50; # 价格等于2.50的产品名、产品价格 select prod_name,prod_price from products where prod_name = "fuses"; # 默认不区分大小写 select prod_name,prod_price from products where prod_price < 10; # 价格小于10的产品名、产品价格 se...
这个ibdata1文件是系统表空间,也是默认的表空间,也是默认的表空间物理文件,也是传说中的共享表空间。 关于这个共享表空间,直观上看,如果这个表空间能为multiple tables.存储数据,那么它就可以被称为共享表空间,所以你可以认为系统表空间是共享表空间。 四、配置sys表空间 系统表空间的数量和大小可以通过启动参数:innod...
select*fromtbwherenamelike"zhang%";select*fromtbwherenamelike"%kai"; 匹配范围值,可以查找某个范围的数据: select*fromtbwhereage>18; 精确匹配某一列并范围匹配另一列,全值匹配第一列,范围匹配第二列: select*fromtbwherename="zhangkai"andage>25; 只访问索引的查询,查询的指定字段是索引列,而不是所有...
❝If multiple rows have identical values in theORDER BYcolumns, the server is free to return those rows in any order, and may do so differently depending on the overall execution plan. In other words, the sort order of those rows is nondeterministic with respect to the nonordered columns...
InnoDB支持多粒度锁(multiple granularity locking),它允许行级锁与表级锁共存,而意向锁就是其中的一种表锁。 1、意向锁的存在是为了协调行锁和表锁的关系,支持多粒度(表锁与行锁)的锁并存。 2、意向锁是一种不与行级锁冲突表级锁,这一点非常重要。 3、表明“某个事务正在某些行持有了锁或该事务准备去持有...
You take those array values and throw them into a string: $string="and t.tag='".$arrayval[0]."' and t.tag='".$arrayval[1]."' and t.tag='".$arrayval[2]."'"; The string would look like below if you echo'ed it out: ...
id=from_user_id;SELECTbalanceINTOto_user_balanceFROMusersWHEREid=to_user_id;IFfrom_user_balance>=amountTHENUPDATEusersSETbalance=balance-amountWHEREid=from_user_id;UPDATEusersSETbalance=balance+amountWHEREid=to_user_id;INSERTINTOtransactions(from_user_id,to_user_id,amount)VALUES(from_user_id,to_...
根据官方的介绍,并结合日志,我们可以看到insert into t8 values (NULL,1,2)在申请一把S Next-key-Lock,显示lock mode S waiting。这里想给大家说明的是在innodb 日志中如果提示 lock mode S /lock mode X ,其实都是gap锁,如果是行记录锁 会提示but not gap ,请读者朋友们在自己分析死锁日志的时候注意。
Table 15.1, “Index Types Per Storage Engine” shows the permissible index type values supported by different storage engines. Where multiple index types are listed, the first one is the default when no index type specifier is given. Storage engines not listed in the table do not support an ...