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- What is the statement to add fields in sql
- The standard SQL statement for adding fields to a data table is [alter table table name add(field field type) [default 'Enter default value'] [null/not null] ;].
- SQL 29174 2020-06-17 16:43:38
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- Redis persistence configuration (picture and text introduction)
- Redis is an open source, highly available non-relational database (NoSQL, not just a database) key-value database written in C language. Different from traditional databases, redis data is stored in memory, so the read and write performance is not generally high and can reach 100,000 operations per second.
- SQL 3118 2020-06-17 16:40:01
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- What is the sql command to delete a table?
- The SQL command to delete a table is [drop table (name of the table to be deleted)], where drop is to delete the entire table to release space, and delete is to delete the contents of the table.
- SQL 47254 2020-06-17 16:35:10
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- What is the command to create a data table in sql
- The command to create a data table in SQL is: [CREATE TABLE table_name (column_name column_type);]. Columns between data tables should be separated by commas in English. SQL statements in data tables are not case-sensitive.
- SQL 18949 2020-06-17 13:43:03
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- What are the common data types in databases?
- Commonly used data types in databases are: 1. Integer data type; 2. Floating point data type, used to store decimals; 3. Binary data type; 4. Logical data type; 5. Character data type, used to store various letters , digital symbols, special symbols.
- SQL 40003 2020-06-16 17:22:16
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- Detailed explanation of sql isnull usage
- In SQL, you can use [isnull] to replace the specified replacement value with NULL. This function is used to replace a NULL value. Its syntax is [ISNULL(check_expression, replacement_value)], and its parameter 1 checks whether it is NULL.
- SQL 5991 2020-06-16 17:15:16
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- What is an inner join?
- Inner joins, the most common equivalent joins, are the earliest joins and are also called ordinary joins or natural joins. The effect is to delete all rows from the result table that do not match rows in other joined tables, so inner joins may lose information.
- SQL 10144 2020-06-16 16:44:05
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- In sql language, what is the command to delete a table?
- In SQL language, the command to delete a table is [drop], and the commands to insert, delete and query data in the table are [INSERT], [UPDATE] and [SELECT] respectively.
- SQL 10031 2020-06-16 15:09:19
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- What should I do if it prompts that restarting the computer fails when installing Server SQL2008?
- The solution to the problem of failure to restart the computer when installing Server SQL2008 is: 1. Open the Registry Editor; 2. Right-click the folder [MSSQLServer] and select [Delete]; 3. Delete the pendingFielRenameOperations option.
- SQL 9085 2020-06-16 11:35:17
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- What are the basic database operation statements?
- The basic operation statements of the database are: 1. To query the database, the statement is [SHOW DATABASES]; 2. To query the structure of the database, the statement is [CREATEDATABASE score]; 3. To create a database, the statement is [DATABASE score DEFAULT CHARSET].
- SQL 14151 2020-06-15 14:05:11
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- What is the difference between hql and sql
- The difference between hql and sql is: 1. The query is different, sql is oriented to database table query, hql is oriented to object query; 2. The judgment conditions are different, the class name followed by from in hql and the class object where are used as conditions for the object's attributes, sql What is followed by from is the table where and then the fields in the table are used to perform conditional queries.
- SQL 16179 2020-06-15 13:19:19
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- Detailed explanation of usage of sql statement case when
- The usage of [case when] in SQL is: 1. Use [case field name when field value then value 1 else value 2 end] to judge the field value; 2. Use [case when condition then value 1 else value 2 end] to judge Field value.
- SQL 53639 2020-06-13 15:08:27
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- MySQL modifies the table structure and its functions of adding, deleting and modifying fields
- mysql is powerful, has many uses, and has many unique uses. This article introduces in detail the MySQL table structure modification and its functions of adding, deleting, and modifying fields. I hope it will help everyone.
- SQL 4031 2020-06-12 09:00:38
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- What is the usage of SQL Union?
- Union is a SQL operator used to combine the results of multiple SELECT statements into a result set. Its syntax is "UNION ALL SELECT * FROM TableB UNION SELECT * FROM TableC".
- SQL 10077 2020-06-09 16:21:31
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- How to use like in sql
- In SQL, like uses wildcards to compare a value with similar values. Its usage is: 1. Percent wildcard character, the syntax is [WHERE SALARY LIKE '200%']; 2. Percent wildcard character, the syntax is [WHERE SALARY] LIKE '_2%3'].
- SQL 21016 2020-06-09 15:40:32
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