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金沙国际官网Mysql索引使用,sqlserver系统函数教程

发布时间:2019-11-06 12:29编辑:数据库浏览(161)

    摘要: 下文收集了sqlserver函数教程,为每一个函数都进行了相关举例说明,

        There're two kinds of intention locks in InnoDB:

    小疑问:

    sqlserver聚合函数教程:
    mssql sqlserver avg聚合函数使用简介
    mssql sqlserver CHECKSUM_AGG聚合函数使用简介
    mssql sqlserver count聚合函数使用简介
    mssql sqlserver count_big聚合函数使用简介
    mssql sqlserver grouping聚合函数使用简介
    mssql sqlserver grouping_id聚合函数使用简介
    mssql sqlserver max及min聚合函数使用简介
    mssql sqlserver stdev及stdevp聚合函数使用简介
    mssql sqlserver sum聚合函数使用简介
    mssql sqlserver var及varp聚合函数使用简介
    sqlserver分析函数教程:
    mssql sqlserver CUME_DIST分析函数使用简介
    mssql sqlserver CUME_DIST分析函数原理说明
    mssql sqlserver FIRST_VALUE LAST_VALUE分析函数使用简介
    mssql sqlserver LAG lead分析函数使用简介
    mssql sqlserver PERCENTILE_CONT分析函数使用简介
    mssql sqlserver PERCENTILE_DISC分析函数使用简介
    mssql sqlserver PERCENT_RANK分析函数使用简介
    sqlserver系统全局变量教程:
    mssql sqlserver @@DBTS全局变量简介
    mssql sqlserver @@LANGID全局变量简介
    mssql sqlserver @@LOCK_TIMEOUT全局变量简介
    mssql sqlserver @@MAX_CONNECTIONS全局变量简介
    mssql sqlserver @@MAX_PRECISION全局变量简介
    mssql sqlserver @@NESTLEVEL全局变量简介
    mssql sqlserver @@REMSERVER全局变量简介
    mssql sqlserver @@SERVERNAME全局变量简介
    mssql sqlserver @@SERVICENAME全局变量简介
    mssql sqlserver @@SPID全局变量简介
    mssql sqlserver @@VERSION全局变量简介
    sqlserver数值类型转换函数教程:
    mssql sqlserver cast数值转换函数用法简介
    mssql sqlserver cast及convert数值转换函数用法简介
    mssql sqlserver parse数值转换函数用法简介
    mssql sqlserver TRY_CAST数值转换函数用法简介
    mssql sqlserver TRY_CONVERT数值转换函数用法简介
    mssql sqlserver TRY_PARSE数值转换函数用法简介
    sqlserver循环相关类函数教程:
    mssql sqlserver @@CURSOR_ROWS循环相关类函数用法简介
    mssql sqlserver @@FETCH_STATUS循环相关类函数用法简介
    mssql sqlserver CURSOR_STATUS循环相关类函数用法简介
    mssql sqlserver_sql流程控制语句while循环关键字用法简介
    mssql sqlserver 模拟for循环的写法
    mssql sqlserver 遍历循环的新方法
    sqlserver数据类型相关函数教程:
    mssql sqlserver DATALENGTH数据类型相关函数用法简介
    mssql sqlserver IDENT_CURRENT数据类型相关函数用法简介
    mssql sqlserver IDENT_INCR数据类型相关函数用法简介
    mssql sqlserver IDENT_SEED数据类型相关函数用法简介
    mssql sqlserver IDENTITY数据类型相关函数用法简介
    mssql sqlserver SQL_VARIANT_PROPERTY数据类型相关函数用法简介
    sqlserver 时间及日期相关函数教程:
    mssql sqlserver @@DATEFIRST时间及日期相关函数用法简介
    mssql sqlserver CURRENT_TIMESTAMP时间及日期相关函数用法简介
    mssql sqlserver DATEADD时间及日期相关函数用法简介
    mssql sqlserver DATEDIFF时间及日期相关函数用法简介
    mssql sqlserver DATEDIFF_BIG时间及日期相关函数用法简介
    mssql sqlserver DATEFROMPARTS时间及日期相关函数用法简介
    mssql sqlserver DATENAME时间及日期相关函数用法简介
    mssql sqlserver DATEPART时间及日期相关函数用法简介
    mssql sqlserver DATETIME2FROMPARTS时间及日期相关函数用法简介
    mssql sqlserver DATETIMEFROMPARTS时间及日期相关函数用法简介
    mssql sqlserver DATETIMEOFFSETFROMPARTS时间及日期相关函数用法简介
    mssql sqlserver DAY时间及日期相关函数用法简介
    mssql sqlserver EOMONTH时间及日期相关函数用法简介
    mssql sqlserver GETDATE时间及日期相关函数用法简介
    mssql sqlserver GETUTCDATE时间及日期相关函数用法简介
    mssql sqlserver ISDATE时间及日期相关函数用法简介
    mssql sqlserver MONTH时间及日期相关函数用法简介
    mssql sqlserver SMALLDATETIMEFROMPARTS时间及日期相关函数用法简介
    mssql sqlserver SWITCHOFFSET时间及日期相关函数用法简介
    mssql sqlserver SYSDATETIME时间及日期相关函数用法简介
    mssql sqlserver SYSDATETIMEOFFSET时间及日期相关函数用法简介
    mssql sqlserver SYSUTCDATETIME时间及日期相关函数用法简介
    mssql sqlserver TIMEFROMPARTS时间及日期相关函数用法简介
    mssql sqlserver TODATETIMEOFFSET时间及日期相关函数用法简介
    mssql sqlserver YEAR时间及日期相关函数用法简介
    mssql sql server 常用日期转换方法分享 (convert datetime)
    sqlserver JSON相关函数教程:
    mssql sqlserver ISJSON相关函数用法简介
    sqlserver 数学函数教程:
    mssql sqlserver ABS数学函数用法简介
    mssql sqlserver ACOS数学函数用法简介
    mssql sqlserver ASIN数学函数用法简介
    mssql sqlserver ATAN数学函数用法简介
    mssql sqlserver ATN2数学函数用法简介
    mssql sqlserver CEILING数学函数用法简介
    mssql sqlserver COS数学函数用法简介
    mssql sqlserver COT数学函数用法简介
    mssql sqlserver DEGREES数学函数用法简介
    mssql sqlserver EXP数学函数用法简介
    mssql sqlserver FLOOR数学函数用法简介
    mssql sqlserver LOG数学函数用法简介
    mssql sqlserver LOG10数学函数用法简介
    mssql sqlserver PI数学函数用法简介
    mssql sqlserver POWER数学函数用法简介
    mssql sqlserver RADIANS数学函数用法简介
    mssql sqlserver RAND数学函数用法简介
    mssql sqlserver ROUND数学函数用法简介
    mssql sqlserver SIGN数学函数用法简介
    mssql sqlserver SIN数学函数用法简介
    mssql sqlserver SQRT数学函数用法简介
    mssql sqlserver SQUARE数学函数用法简介
    mssql sqlserver TAN数学函数用法简介
    sqlserver 逻辑函数教程:
    mssql sqlserver CHOOSE逻辑函数用法简介
    mssql sqlserver IIF逻辑函数用法简介
    sqlserver 元数据教程:
    mssql sqlserver @@PROCID元数据用法简介
    mssql sqlserver APP_NAME元数据用法简介
    mssql sqlserver ASSEMBLYPROPERTY元数据用法简介
    mssql sqlserver COL_LENGTH COL_NAME COLUMNPROPERTY元数据用法简介
    mssql sqlserver DATABASE_PRINCIPAL_ID元数据用法简介
    mssql sqlserver DATABASEPROPERTYEX元数据用法简介
    mssql sqlserver DB_ID DB_NAME元数据用法简介
    mssql sqlserver FILE_ID元数据用法简介
    mssql sqlserver FILE_IDEX元数据用法简介
    mssql sqlserver FILE_NAME元数据用法简介
    mssql sqlserver FILEGROUP_ID元数据用法简介
    mssql sqlserver FILEGROUP_NAME元数据用法简介
    mssql sqlserver FILEGROUPPROPERTY元数据用法简介
    mssql sqlserver FILEPROPERTY元数据用法简介
    mssql sqlserver FULLTEXTCATALOGPROPERTY元数据用法简介
    mssql sqlserver FULLTEXTSERVICEPROPERTY元数据用法简介
    mssql sqlserver INDEX_COL元数据用法简介
    mssql sqlserver INDEXKEY_PROPERTY元数据用法简介
    mssql sqlserver INDEXPROPERTY元数据用法简介
    mssql sqlserver OBJECT_DEFINITION元数据用法简介
    mssql sqlserver OBJECT_ID元数据用法简介
    mssql sqlserver OBJECT_NAME元数据用法简介
    mssql sqlserver OBJECT_SCHEMA_NAME元数据用法简介
    mssql sqlserver ORIGINAL_DB_NAME元数据用法简介
    mssql sqlserver PARSENAME元数据用法简介
    mssql sqlserver SCHEMA_ID元数据用法简介
    mssql sqlserver SCHEMA_NAME元数据用法简介
    mssql sqlserver SCOPE_IDENTITY元数据用法简介
    mssql sqlserver SERVERPROPERTY元数据用法简介
    mssql sqlserver STATS_DATE元数据用法简介
    mssql sqlserver TYPE_ID元数据用法简介
    mssql sqlserver TYPE_NAME元数据用法简介
    mssql sqlserver TYPEPROPERTY元数据用法简介
    sqlserver 排名函数教程:
    mssql sqlserver 分组排序函数row_number、rank、dense_rank用法简介及说明
    row_number() rank() dense_rank() 排名函数的用途及区别
    sqlserver 复制函数教程:
    mssql sqlserver PUBLISHINGSERVERNAME 关键字功能说明
    sqlserver 集合获取函数:
    mssql sqlserver OPENDATASOURCE集合获取函数简介
    mssql sqlserver OPENJSON集合获取函数简介
    mssql sqlserver OPENQUERY集合获取函数简介
    mssql sqlserver OPENROWSET集合获取函数简介
    mssql sqlserver OPENXML集合获取函数简介
    sqlserver字符串函数教程:
    mssql sqlserver ASCII字符串函数简介
    mssql sqlserver CHAR字符串函数简介
    mssql sqlserver CHARINDEX字符串函数简介
    mssql sqlserver CONCAT字符串函数简介
    mssql sqlserver CONCAT_WS字符串函数简介
    mssql sqlserver DIFFERENCE字符串函数简介
    mssql sqlserver FORMAT字符串函数简介
    mssql sqlserver LEFT字符串函数简介
    mssql sqlserver LEN字符串函数简介
    mssql sqlserver LOWER字符串函数简介
    mssql sqlserver LTRIM字符串函数简介
    mssql sqlserver NCHAR字符串函数简介
    mssql sqlserver PATINDEX字符串函数简介
    mssql sqlserver QUOTENAME字符串函数简介
    mssql sqlserver REPLACE字符串函数简介
    mssql sqlserver REPLICATE字符串函数简介
    mssql sqlserver REVERSE字符串函数简介
    mssql sqlserver RIGHT字符串函数简介
    mssql sqlserver RTRIM字符串函数简介
    mssql sqlserver SOUNDEX字符串函数简介
    mssql sqlserver SPACE字符串函数简介
    mssql sqlserver STR字符串函数简介
    mssql sqlserver错误修复-“string_split无效的对象名称”
    mssql sqlserver STUFF字符串函数简介
    mssql sqlserver SUBSTRING字符串函数简介
    mssql sqlserver UNICODE字符串函数简介
    mssql sqlserver UPPER字符串函数简介
    sqlserver系统函数教程:
    mssql sqlserver $PARTITION系统函数简介
    mssql sqlserver @@ERROR系统函数简介
    mssql sqlserver @@IDENTITY系统函数简介
    mssql sqlserver @@PACK_RECEIVED系统函数简介
    mssql sqlserver @@ROWCOUNT系统函数简介
    mssql sqlserver @@TRANCOUNT系统函数简介
    mssql sqlserver BINARY_CHECKSUM系统函数简介
    mssql sqlserver CONNECTIONPROPERTY系统函数简介
    mssql sqlserver HOST_ID host_name系统函数简介
    mssql sqlserver ISNULL系统函数简介
    mssql sqlserver ISNUMERIC系统函数简介
    mssql sqlserver NEWID系统函数简介
    mssql sqlserver ROWCOUNT_BIG系统函数简介
    sqlserver 系统统计函数:
    mssql sqlserver @@CONNECTIONS系统统计函数简介
    mssql sqlserver @@CPU_BUSY系统统计函数简介
    mssql sqlserver @@IDLE系统统计函数简介
    mssql sqlserver @@IO_BUSY系统统计函数简介
    mssql sqlserver @@PACK_SENT系统统计函数简介
    mssql sqlserver @@PACKET_ERRORS系统统计函数简介
    mssql sqlserver @@TIMETICKS系统统计函数简介
    mssql sqlserver @@TOTAL_ERRORS系统统计函数简介
    mssql sqlserver @@TOTAL_READ系统统计函数简介
    mssql sqlserver @@TOTAL_WRITE系统统计函数简介

     

       作用:规定定义为唯一索引的列,不允许包含重复项但允许为NULL

    如下所示:

     

      3. 外界进行修改时添加

     

    索引是由什么组成的?原文中具有代表性的一部分。

     

        唯一索引无法成为外键,而且一张表可以有多个唯一索引。

    *Examples*

     

      X IX S IS
    X Conflict Conflict Conflict Conflict
    IX Conflict Compatible Conflict Compatible
    S Conflict Conflict Compatible Compatible
    IS Conflict Compatible Compatible Compatible

        作用:起普通目录的作用,没有加上任何限制条件,一个表可以存在多个普通索引

    ***4. Inert intention locks test.***

        作用:对于多条件查询会显著提高速度,但是存储该索引的代价也很大

      1 //Session 1:
      2 zlm@192.168.56.100:3306 [(zlm)]>select @@transaction_isolation;
      3 +-------------------------+
      4 | @@transaction_isolation |
      5 +-------------------------+
      6 | REPEATABLE-READ         |
      7 +-------------------------+
      8 1 row in set (0.00 sec)
      9 
     10 zlm@192.168.56.100:3306 [zlm]>begin;select * from t for update;
     11 Query OK, 0 rows affected (0.00 sec)
     12 
     13 +----+------+
     14 | id | name |
     15 +----+------+
     16 |  1 | aaa  |
     17 |  2 | bbb  |
     18 |  4 | ccc  |
     19 |  6 | fff  |
     20 +----+------+
     21 4 rows in set (0.00 sec)
     22 
     23 //Session 2:
     24 zlm@192.168.56.100:3306 [(zlm)]>select @@transaction_isolation;
     25 +-------------------------+
     26 | @@transaction_isolation |
     27 +-------------------------+
     28 | REPEATABLE-READ         |
     29 +-------------------------+
     30 1 row in set (0.00 sec)
     31 
     32 zlm@192.168.56.100:3306 [(none)]>begin;insert into zlm.t values(5,'eee');
     33 Query OK, 0 rows affected (0.00 sec)
     34 
     35 ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction
     36 zlm@192.168.56.100:3306 [(none)]>
     37 
     38 //Check the error log for detail of locks.
     39 [root@zlm1 04:51:25 /data/mysql/mysql3306/data]
     40 #tail -f error.log 
     41 
     42 ...
     43 ------------
     44 TRANSACTIONS
     45 ------------
     46 Trx id counter 2996022
     47 Purge done for trx's n:o < 2996020 undo n:o < 0 state: running but idle
     48 History list length 15
     49 LIST OF TRANSACTIONS FOR EACH SESSION:
     50 ---TRANSACTION 2996021, ACTIVE 13 sec inserting
     51 mysql tables in use 1, locked 1
     52 LOCK WAIT 2 lock struct(s), heap size 1136, 1 row lock(s) //The two lock structs were intention lock("IX") and insert intention lock.
     53 MySQL thread id 318, OS thread handle 140311522375424, query id 12700 zlm1 192.168.56.100 zlm update
     54 insert into zlm.t values(5,'eee')
     55 ------- TRX HAS BEEN WAITING 13 SEC FOR THIS LOCK TO BE GRANTED:
     56 RECORD LOCKS space id 175 page no 3 n bits 72 index GEN_CLUST_INDEX of table `zlm`.`t` trx id 2996021 lock_mode X insert intention waiting
     57 Record lock, heap no 1 PHYSICAL RECORD: n_fields 1; compact format; info bits 0
     58  0: len 8; hex 73757072656d756d; asc supremum;; //Session 1 holds all "X" record locks of table "t".So it showed supremum what means the gap is infinite and no record can be inserted into the table at all.
     59 
     60 ------------------
     61 TABLE LOCK table `zlm`.`t` trx id 2996021 lock mode IX //The "IX" intention lock of session 2.
     62 RECORD LOCKS space id 175 page no 3 n bits 72 index GEN_CLUST_INDEX of table `zlm`.`t` trx id 2996021 lock_mode X insert intention waiting
     63 Record lock, heap no 1 PHYSICAL RECORD: n_fields 1; compact format; info bits 0
     64  0: len 8; hex 73757072656d756d; asc supremum;;
     65 
     66 ---TRANSACTION 2996020, ACTIVE 255 sec
     67 2 lock struct(s), heap size 1136, 5 row lock(s)
     68 MySQL thread id 316, OS thread handle 140311522174720, query id 12450 zlm1 192.168.56.100 zlm
     69 TABLE LOCK table `zlm`.`t` trx id 2996020 lock mode IX //The "IX" intention lock of session 1.
     70 RECORD LOCKS space id 175 page no 3 n bits 72 index GEN_CLUST_INDEX of table `zlm`.`t` trx id 2996020 lock_mode X
     71 Record lock, heap no 1 PHYSICAL RECORD: n_fields 1; compact format; info bits 0
     72  0: len 8; hex 73757072656d756d; asc supremum;;
     73 
     74 Record lock, heap no 2 PHYSICAL RECORD: n_fields 5; compact format; info bits 0
     75  0: len 6; hex 000000000700; asc       ;;
     76  1: len 6; hex 0000002db708; asc    -  ;;
     77  2: len 7; hex a8000002610110; asc     a  ;;
     78  3: len 4; hex 80000001; asc     ;;
     79  4: len 10; hex 61616120202020202020; asc aaa       ;;
     80 
     81 Record lock, heap no 3 PHYSICAL RECORD: n_fields 5; compact format; info bits 0
     82  0: len 6; hex 000000000701; asc       ;;
     83  1: len 6; hex 0000002db708; asc    -  ;;
     84  2: len 7; hex a800000261011f; asc     a  ;;
     85  3: len 4; hex 80000002; asc     ;;
     86  4: len 10; hex 62626220202020202020; asc bbb       ;;
     87 
     88 Record lock, heap no 4 PHYSICAL RECORD: n_fields 5; compact format; info bits 0
     89  0: len 6; hex 000000000702; asc       ;;
     90  1: len 6; hex 0000002db708; asc    -  ;;
     91  2: len 7; hex a800000261012e; asc     a .;;
     92  3: len 4; hex 80000004; asc     ;;
     93  4: len 10; hex 63636320202020202020; asc ccc       ;;
     94 
     95 Record lock, heap no 5 PHYSICAL RECORD: n_fields 5; compact format; info bits 0
     96  0: len 6; hex 000000000703; asc       ;;
     97  1: len 6; hex 0000002db721; asc    - !;;
     98  2: len 7; hex 360000012c2a35; asc 6   ,*5;;
     99  3: len 4; hex 80000006; asc     ;;
    100  4: len 10; hex 66666620202020202020; asc fff       ;;
    101  
    102  ...
    103 ----------------------------
    104 END OF INNODB MONITOR OUTPUT
    105 ============================
    106 ^C
    107 
    108 //Session 2 meant to get an insert intention lock when it was executing "insert into xxx" but waited until timeout.
    109 //Whatif we only lock a certain record,what will session do then?Let's see below.
    110 
    111 //Session 1:
    112 zlm@192.168.56.100:3306 [zlm]>begin;select * from t where id=4 for update;
    113 Query OK, 0 rows affected (0.00 sec)
    114 
    115 +----+------+
    116 | id | name |
    117 +----+------+
    118 |  4 | ccc  |
    119 +----+------+
    120 1 row in set (0.00 sec)
    121 
    122 //Session 2:
    123 zlm@192.168.56.100:3306 [(none)]>begin;insert into zlm.t values(3,'ccc');
    124 ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction
    125 zlm@192.168.56.100:3306 [(none)]>
    126 
    127 //Check error log again.
    128 [root@zlm1 05:06:19 /data/mysql/mysql3306/data]
    129 #tail -f error.log 
    130 
    131 ...
    132 ------------
    133 TRANSACTIONS
    134 ------------
    135 Trx id counter 2996025
    136 Purge done for trx's n:o < 2996020 undo n:o < 0 state: running but idle
    137 History list length 15
    138 LIST OF TRANSACTIONS FOR EACH SESSION:
    139 ---TRANSACTION 2996024, ACTIVE 9 sec inserting
    140 mysql tables in use 1, locked 1
    141 LOCK WAIT 2 lock struct(s), heap size 1136, 1 row lock(s), undo log entries 1
    142 MySQL thread id 376, OS thread handle 140311521974016, query id 14398 zlm1 192.168.56.100 zlm update
    143 insert into zlm.t values(3,'ccc')
    144 ------- TRX HAS BEEN WAITING 9 SEC FOR THIS LOCK TO BE GRANTED:
    145 RECORD LOCKS space id 175 page no 4 n bits 72 index id of table `zlm`.`t` trx id 2996024 lock_mode X locks gap before rec insert intention waiting
    146 Record lock, heap no 4 PHYSICAL RECORD: n_fields 2; compact format; info bits 0
    147  0: len 4; hex 80000004; asc     ;;
    148  1: len 6; hex 000000000702; asc       ;;
    149 
    150 ------------------
    151 TABLE LOCK table `zlm`.`t` trx id 2996024 lock mode IX
    152 RECORD LOCKS space id 175 page no 4 n bits 72 index id of table `zlm`.`t` trx id 2996024 lock_mode X locks gap before rec insert intention waiting
    153 Record lock, heap no 4 PHYSICAL RECORD: n_fields 2; compact format; info bits 0
    154  0: len 4; hex 80000004; asc     ;;
    155  1: len 6; hex 000000000702; asc       ;;
    156 
    157 ---TRANSACTION 2996023, ACTIVE 28 sec
    158 4 lock struct(s), heap size 1136, 3 row lock(s)
    159 MySQL thread id 374, OS thread handle 140311415437056, query id 14377 zlm1 192.168.56.100 zlm
    160 TABLE LOCK table `zlm`.`t` trx id 2996023 lock mode IX
    161 RECORD LOCKS space id 175 page no 4 n bits 72 index id of table `zlm`.`t` trx id 2996023 lock_mode X
    162 Record lock, heap no 4 PHYSICAL RECORD: n_fields 2; compact format; info bits 0
    163  0: len 4; hex 80000004; asc     ;;
    164  1: len 6; hex 000000000702; asc       ;;
    165 
    166 RECORD LOCKS space id 175 page no 3 n bits 72 index GEN_CLUST_INDEX of table `zlm`.`t` trx id 2996023 lock_mode X locks rec but not gap
    167 Record lock, heap no 4 PHYSICAL RECORD: n_fields 5; compact format; info bits 0
    168  0: len 6; hex 000000000702; asc       ;;
    169  1: len 6; hex 0000002db708; asc    -  ;;
    170  2: len 7; hex a800000261012e; asc     a .;;
    171  3: len 4; hex 80000004; asc     ;;
    172  4: len 10; hex 63636320202020202020; asc ccc       ;;
    173 
    174 RECORD LOCKS space id 175 page no 4 n bits 72 index id of table `zlm`.`t` trx id 2996023 lock_mode X locks gap before rec
    175 Record lock, heap no 5 PHYSICAL RECORD: n_fields 2; compact format; info bits 0
    176  0: len 4; hex 80000006; asc     ;;
    177  1: len 6; hex 000000000703; asc       ;;
    178 
    179 //The locks seem to be more and more complicated.
    180 //Session 1(TRANSACTION 2996023) holded an "IX" intention lock,a "X" record lock,two gap locks.
    181 //Session 2(TRANSACTION 2996024) asked for holded an "IX" intention lock and asked for an intert intention lock which was relevant with the gap before the record it meant to insert.The transaction of session 2 waited until timeout.
    

          3. 模止原则。即在你的查询条件中,设置 “列2” 为“xx%” 的模糊查询,那么索引会将“列2”之后的所有列舍去。

    1. Intention Locks

      全文索引,

    *Summary*

    多说一点:

    **2. I**nsert In***tention Locks***

     

    • *

      全文索引和唯一索引的区别:

        Notice,any transaction who want to get row-level lock(shared or exclusive lock) on a record in a table must get the intention locks first.Generally speaking,S row-level lock is versus IS while X row-level lock is versus IX.There conflict relationship shows below.

    索引有五种分类:  

    *2. Intention locks test in the same session with "innodb_status_output_locks=on".*

        关键词 Key (列1,列2 ...)

        Last night one buddy in tech wechat group asked "what's intention locks of InnoDB?"Thus,I'm gonna say someting about it.As we all know,there're various types of lock in InnoDB engine such as record locks,gap locks,next key locks and so forth.Intention locks is another kind of granularity of lock of InnoDB.

        SELECT * FROM user WHERE MATCH (id ) AGAINST ( ' xxx ');

     

        作用:在唯一索引的基础上,不允许为NULL

     

      主键索引,

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    关键词:

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