MySQL

JDBC connect MySQL database Timezone Time zone issues FAQ

Cause of the problem ： Database driven mysql-connector-java8.0.16.jar The version of is higher , Here we use 8.0.16 Explain the problem descriptio...
2021-03-26 13:27 views 199

mysql Several implementations of obtaining the latest data according to a certain field

In actual business , We often encounter the problem of how to get the latest data from the same value of the same field . After self accumulation ...
2021-02-23 22:32 views 13

Cause: java.sql.SQLSyntaxErrorException: Unknown column ‘name‘ in ‘field

### Cause: java.sql.SQLSyntaxErrorException: Unknown column 'name' in 'field list'; bad SQL grammar []; nested exception is java.sql.SQLSyntaxError...
2021-02-21 22:12 views 359

mysql Batch execute statement _mysql Batch execution sql sentence

tablename Access database :SELECT iif(len(field)>2,left(field,2)+'...',field) FROM tablename; Conn.Execute explain Execute method This met...
2021-02-18 21:01 views 42

mysql Index failure _ Under what circumstances mysql The index will fail ?

mysql Several cases of index failure ：1, Conditions include or, Even if there is conditional indexing, it will not be used ;2, For multi column ind...
2021-02-08 16:56 views 38

mysql operation begin command _MySQL Basic operation

MySQL1, Connected data volume mysql -u username -p Enter after entering the command , display Enter password: Just enter the password .username...
2021-02-08 10:31 views 14

mysql The index is stored on disk _MySQL—— The index is stored on disk

usually , The index itself is large , Cannot be completely stored in memory , Therefore, indexes are usually stored on disk as index files . under...
2021-02-07 11:06 views 61

Oracle2021 Annual safety warning ,8 There are two security vulnerabilities that need attention

| news flash Oracle company to 2021 year 1 month 19 day , The first annual security alert was issued . among , yes 8 Safety warnings an...
2021-01-20 13:57 views 21

mysql How is the index checked _mysql-- Indexes （ query ）

What is an index if there is no index , The number of scanned records is greater than the number of indexed records. The index stores the value of...
2021-01-19 17:09 views 21

mysql Trigger instance update_mysql Trigger example description

Triggers are a special kind of transactions , Can monitor certain data operations (insert/update/delete), And trigger relevant operations (insert...
2021-01-19 15:15 views 17
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