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mysql简单语法(MySQL simple syntax)
mysql简单语法(MySQL simple syntax)
MySQL syntax statement Daquan
First, the SQL crash
Structured query language (SQL) is a standard language for querying relational databases. It includes a number of keywords and consistent syntax to facilitate the creation and manipulation of database components such as tables, indexes, fields, and so on.
Here are some important SQL quick references about the syntax of SQL and the features added to the standard SQL. Please consult the MySQL manual.
1. create table
Tables are one of the most basic elements of a database. Tables and tables can be independent of each other or they can be related to each other. The basic syntax for creating tables is as follows:
Create table table_name
(column_name data invalid, {identity, |null|not, null},
... )
Where parameters table_name and column_name must satisfy the requirements of the identifier (identifier) in the user database, the parameter data is invalid, a standard SQL type or the type supplied by the user database. Users use the non-null clause to enter data for each field.
Create table has several other options, such as creating temporary tables and using the select clause to read certain fields from other tables, to form new tables, and so on. Also, when creating a table, you can use PRIMARY, KEY, KEY, INDEX, and other identifiers to set some fields as primary keys or indexes.
Pay attention to your handwriting:
List the complete fields in a pair of parentheses.
Field names are separated by commas.
Add a space after the comma between the field names.
Do not use commas after the last field name.
All SQL statements end with a semicolon.
Cases:
Mysql, CREATE, TABLE, test (blob_col, BLOB, index (blob_col (10)));
2. create index
An index used to query a database. A general database is built with a variety of indexing schemes, each of which is well suited to a particular query class. Indexes can speed up the query process for databases. The basic syntax for creating indexes is as follows:
Create
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