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- What command is used to create a database in mysql
- The command to create a database in MySQL is CREATE DATABASE database_name;. You need to specify the name of the database to be created. For example, to create a database named "my_database", use CREATE DATABASE my_database;.
- Mysql Tutorial 1130 2024-05-01 21:06:33
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- What does value mean in mysql
- VALUE keyword in MySQL: 1. Get column value: SELECT value FROM table_name WHERE column_name = value; 2. Set column value: UPDATE table_name SET column_name = value WHERE condition.
- Mysql Tutorial 790 2024-05-01 21:03:53
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- Usage of decode function in mysql
- The DECODE function maps values based on a given condition: an expression is evaluated and matched against the condition value. If there is a match, the corresponding result value is returned; if there is no match, the default value is returned.
- Mysql Tutorial 396 2024-05-01 21:03:32
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- Does null take up space in mysql?
- Null takes up no space in MySQL. It only represents missing data, stored as the special value NULL, without taking up any actual storage space. Its storage mechanism uses bitmaps to set bits according to whether the field is Null, saving space, optimizing query performance, and avoiding data integrity issues. Note that the Null value is not equal to the empty string or the zero value, which takes up storage space.
- Mysql Tutorial 415 2024-05-01 21:01:16
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- The difference between null and empty values in mysql
- NULL represents an unknown and meaningless value, while null represents an unassigned or uninitialized value. The differences between the two are: semantic differences, database processing methods, query optimization impact, data integrity impact, which can be distinguished through the operators provided by MySQL.
- Mysql Tutorial 570 2024-05-01 21:00:54
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- Why does the COALESCE function in mysql fail?
- The reason why the COALESCE function in MySQL fails is that all the parameters are NULL. The parameter type is incompatible and the NULL expression is passed. A minor error.
- Mysql Tutorial 502 2024-05-01 21:00:32
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- What does from dual mean in mysql
- FROM DUAL is used in MySQL to retrieve data from the single-row virtual table DUAL. It is often used to get the current date and time, database version, or as a placeholder in a query or to execute a DDL statement.
- Mysql Tutorial 820 2024-05-01 20:58:02
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- Can from be followed by case in mysql?
- Yes, MySQL allows the use of CASE expressions in the FROM clause to select specific rows, the syntax is: SELECT ... FROM table_name WHERE <filter_condition> AND CASE WHEN <condition1> THEN <value1> WHEN <condition2> THEN <value2> ELSE <default_value> END AS <alias> where <fil
- Mysql Tutorial 997 2024-05-01 20:57:41
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- What does whwre mean in mysql?
- The WHERE clause is used to specify filter conditions in MySQL queries to filter matching records from the result set. Its syntax structure is: SELECT * FROM table_name WHERE condition;. The WHERE clause can be used to display only records that meet certain criteria, exclude unnecessary records, and group or sort query results. A condition consists of an operator and an operand, which can be a column name, a constant, or an expression. Operators include "=", "!=", ">", "<", ">=", and "<=". Multiple conditions can be connected using logical operators (AND, OR).
- Mysql Tutorial 993 2024-05-01 20:57:17
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- How to correct field errors in mysql
- "Unknown column" errors with the FIELD() function in MySQL are usually caused by misspelling of the column name, non-existence of the column, or insufficient permissions. Fix: Check the spelling of the column name in the FIELD() function. Use the SHOW COLUMNS query to confirm whether the column exists. Use a SELECT query to check access to a column. If the above steps cannot solve the problem, it is recommended to back up the data and try to repair the table or database.
- Mysql Tutorial 823 2024-05-01 20:54:39
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- How to calculate the length of enum in mysql
- The length of the ENUM data type in MySQL depends on the number of characters stored and the number of bytes in the character set. The calculation formula is: number of characters stored × number of bytes in the character set.
- Mysql Tutorial 983 2024-05-01 20:54:15
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- What does or mean in mysql
- In MySQL, the OR operator (||) joins multiple conditions and returns true as long as one of the conditions is true. It is used to find data that meets multiple criteria, combine subquery results, and create complex search criteria.
- Mysql Tutorial 499 2024-05-01 20:51:50
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- What does as mean in mysql
- ASAS in MySQL is a keyword used to create an alias or specify a new table name. It improves readability, avoids ambiguity, performs temporary renaming, and creates table aliases. Aliases created using AS are only valid within the current query by default, but permanent aliases can be created using the CREATE ALIAS statement.
- Mysql Tutorial 998 2024-05-01 20:49:01
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- What does acid in mysql mean?
- ACID in MySQL includes atomicity, consistency, isolation, and durability. Atomicity ensures that all transactions succeed or fail; consistency ensures that the database state remains consistent before and after the transaction; isolation ensures that concurrent transactions do not affect each other; and durability ensures that submitted modifications are permanently saved.
- Mysql Tutorial 463 2024-05-01 20:48:39
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- What does analyze in mysql do?
- The MySQL ANALYZE command updates table statistics to optimize query performance, including statistics updates, query optimizer improvements, and space release. It works by scanning table data to calculate the number of rows, the number of DISTINCT values, and the distribution of values to generate a more optimized query plan. Perform ANALYZE on frequently queried tables regularly and analyze only key columns for best practices.
- Mysql Tutorial 842 2024-05-01 20:48:14
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