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https://dev.mysql.com/doc/refman/5.7/en/alter-table-problems.html
If you get a duplicate-key error when using ALTER TABLE to change the character set or collation of a character column, the cause is either that the new column collation maps two keys to the same value or that the table is corrupted. In the latter ...
https://dev.mysql.com/doc/refman/5.7/en/csv-storage-engine.html
When you create a CSV table, the server creates a table format file in the database directory. If you examine the test.CSV file in the database directory created by executing the preceding statements, its contents should look like this: "1","record ... The CSV storage engine stores data in text files using comma-separated values ...
https://dev.mysql.com/doc/refman/5.7/en/condition-handling.html
Handlers can be defined for general conditions such as warnings or exceptions, or for specific conditions such as a particular error code. For information about how the server chooses handlers when a condition occurs, see Section 13.6.7.6, “Scope ... Conditions may arise during stored program execution that require special handling, such as exiting the current program block or continuing ...
https://dev.mysql.com/doc/refman/5.7/en/create-table-like.html
LIKE to create an empty table based on the definition of another table, including any column attributes and indexes defined in the original table: CREATE TABLE new_tbl LIKE orig_tbl; The copy is created using the same version of the table storage ...
https://dev.mysql.com/doc/refman/5.7/en/drop-view.html
To avoid this failure scenario, use IF EXISTS syntax in DROP VIEW statements to prevent an error from occurring for views that do not exist. The IF EXISTS clause prevents an error from occurring for views that don't exist. When this clause is given, ...If any views named in the argument list do not exist, the statement returns an error indicating by name which nonexisting views it was unable to drop, but also drops all views in the list that do ...
https://dev.mysql.com/doc/refman/5.7/en/estimating-performance.html
In most cases, you can estimate query performance by counting disk seeks. For small tables, you can usually find a row in one disk seek (because the index is probably cached). For bigger tables, you can estimate that, using B-tree indexes, you need ...In MySQL, an index block is usually 1,024 bytes and the data pointer is usually four ...
https://dev.mysql.com/doc/refman/5.7/en/information-schema-variables-table.html
Note The value of the show_compatibility_56 system variable affects the information available from the tables described here. For details, see the description of that variable in Section 5.1.7, “Server System Variables”. Note Information ...
https://dev.mysql.com/doc/refman/5.7/en/innodb-error-handling.html
A lock wait timeout causes InnoDB to roll back the current statement (the statement that was waiting for the lock and encountered the timeout). Both deadlocks and lock wait timeouts are normal on busy servers and it is necessary for applications to ...InnoDB sometimes rolls back only the statement that failed, other times it rolls back the entire ...
https://dev.mysql.com/doc/refman/5.7/en/myisam-check.html
It first checks all index entries for errors and then reads through all rows. It calculates a checksum for all key values in the rows and verifies that the checksum matches the checksum for the keys in the index tree. It does a check-read of every ... To check a MyISAM table, use the following commands: myisamchk tbl_name This finds 99.99% of all ...
https://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-programs-ndb-perror.html
ndb_perror shows information about an NDB error, given its error code. Added to the MySQL NDB Cluster distribution in NDB 7.6, it is intended as a drop-in replacement for perror --ndb. To make substitution easier in scripts and other applications ...This includes the error message, the type of error, and whether the error is permanent or ...