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https://dev.mysql.com/doc/refman/5.7/en/performance-schema-replication-applier-status-table.html
The maximum number of retries for a given transaction is set by the slave_transaction_retries system variable. The table provides information about general aspects of transaction applier status that are not specific to any thread involved. This ...
https://dev.mysql.com/doc/refman/5.7/en/optimization.html
This chapter explains how to optimize MySQL performance and provides examples. Depending on your job role (developer, DBA, or a combination of both), you might optimize at the level of individual SQL statements, entire applications, a single ...
https://dev.mysql.com/doc/refman/5.7/en/error-creating-innodb.html
If you already created some InnoDB tables, also delete the corresponding .frm files for these tables, and any .ibd files if you are using multiple tablespaces, from the MySQL database directories. The troubleshooting steps for InnoDB I/O problems ...Initialization Problems If something goes wrong when InnoDB attempts to initialize its tablespace or its log files, delete all files created by InnoDB: all ibdata files and all ib_logfile ...
https://dev.mysql.com/doc/refman/5.7/en/innodb-compression-background.html
Data compression enables smaller database size, reduced I/O, and improved throughput, at the small cost of increased CPU utilization. Compression is especially valuable for read-intensive applications, on systems with enough RAM to keep frequently ... Because processors and cache memories have increased in speed more than disk storage devices, many workloads are ...
https://dev.mysql.com/doc/refman/5.7/en/index-btree-hash.html
Understanding the B-tree and hash data structures can help predict how different queries perform on different storage engines that use these data structures in their indexes, particularly for the MEMORY storage engine that lets you choose B-tree or ...In the second statement, only rows with 'Pat' <= key_col < 'Pau' are ...
https://dev.mysql.com/doc/refman/5.7/en/insert-select.html
For example: INSERT INTO tbl_temp2 (fld_id) SELECT tbl_temp1.fld_order_id FROM tbl_temp1 WHERE tbl_temp1.fld_order_id > 100; The following conditions hold for INSERT ... To ensure that the binary log can be used to re-create the original tables, ...
https://dev.mysql.com/doc/refman/5.7/en/loading-tables.html
For missing values (such as unknown sexes or death dates for animals that are still living), you can use NULL values. These are sufficient for the statement to read the file pet.txt properly. See Section 6.1.6, “Security Considerations for LOAD ...
https://dev.mysql.com/doc/refman/5.7/en/numeric-types.html
The keyword INT is a synonym for INTEGER, and the keywords DEC and FIXED are synonyms for DECIMAL. MySQL treats DOUBLE as a synonym for DOUBLE PRECISION (a nonstandard extension). MySQL also treats REAL as a synonym for DOUBLE PRECISION (a ...These ...
https://dev.mysql.com/doc/refman/5.7/en/problems-with-null.html
The concept of the NULL value is a common source of confusion for newcomers to SQL, who often think that NULL is the same thing as an empty string ''. For example, the following statements are completely different: mysql> INSERT INTO my_table ...In ...
https://dev.mysql.com/doc/refman/5.7/en/truncate-table.html
TRUNCATE TABLE can be used with Performance Schema summary tables, but the effect is to reset the summary columns to 0 or NULL, not to remove rows. To achieve high performance, it bypasses the DML method of deleting data. Thus, it cannot be rolled ...Logically, TRUNCATE TABLE is similar to a DELETE statement that deletes all rows, or a sequence of DROP TABLE and CREATE TABLE ...