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https://dev.mysql.com/doc/refman/5.7/en/explain.html
In practice, the DESCRIBE keyword is more often used to obtain information about table structure, whereas EXPLAIN is used to obtain a query execution plan (that is, an explanation of how MySQL would execute a query). The following discussion uses ...
https://dev.mysql.com/doc/refman/5.7/en/optimizing-innodb-storage-layout.html
Use the VARCHAR data type instead of CHAR to store variable-length strings or for columns with many NULL values. A CHAR(N) column always takes N characters to store data, even if the string is shorter or its value is NULL. Once your data reaches a ...
https://dev.mysql.com/doc/refman/5.7/en/arithmetic-functions.html
(See Section 11.1, “Numeric Data Types”.) / Division: mysql> SELECT 3/5; -> 0.60 Division by zero produces a NULL result: mysql> SELECT 102/(1-1); -> NULL A division is calculated with BIGINT arithmetic only if performed in a context where its ... Table 12.9 Arithmetic Operators Name Description %, MOD Modulo operator * Multiplication operator + Addition operator - Minus operator - Change the sign of the argument / Division operator DIV Integer division The usual arithmetic operators are ...
https://dev.mysql.com/doc/refman/5.7/en/date-and-time-types.html
MySQL permits you to store a “zero” value of '0000-00-00' as a “dummy date.” In some cases, this is more convenient than using NULL values, and uses less data and index space. “Zero” date or time values used through Connector/ODBC are ...
https://dev.mysql.com/doc/refman/5.7/en/fulltext-search-mecab.html
The mecab_rc_file option is not recognized by MySQL until the MeCaB parser plugin is installed but it must be set before attempting to install the MeCaB parser plugin. The built-in MySQL full-text parser uses the white space between words as a ...
https://dev.mysql.com/doc/refman/5.7/en/constraint-foreign-key.html
The available referential actions are RESTRICT (the default), CASCADE, SET NULL, and NO ACTION. Foreign keys let you cross-reference related data across tables, and foreign key constraints help keep this spread-out data consistent. MySQL supports ...
https://dev.mysql.com/doc/refman/5.7/en/csv-storage-engine.html
The CSV storage engine stores data in text files using comma-separated values format. The CSV storage engine is always compiled into the MySQL server. To examine the source for the CSV engine, look in the storage/csv directory of a MySQL source ...
https://dev.mysql.com/doc/refman/5.7/en/example-maximum-column-group-row.html
Task: For each article, find the dealer or dealers with the most expensive price. Other possibilities for solving the problem are to use an uncorrelated subquery in the FROM clause or a LEFT JOIN.
https://dev.mysql.com/doc/refman/5.7/en/gis-property-functions.html
Such functions return NULL if the argument is of an incorrect geometry type. For example, the ST_Area() polygon function returns NULL if the object type is neither Polygon nor MultiPolygon. Each function that belongs to this group takes a geometry ...
https://dev.mysql.com/doc/refman/5.7/en/group-replication-adding-instances.html
At this point, the group has one member in it, server s1, which has some data in it. It is now time to expand the group by adding the other two servers configured previously. 17.2.1.6.1 Adding a Second Instance In order to add a second instance, ...