:SQL syntax overview

This topic describes the SQL syntax and operations in PolarDB-X.

PolarDB-X is highly compatible with the SQL syntax in MySQL. The syntax characteristics of PolarDB-X are not the same as those of MySQL due to the architecture differences between distributed databases and single-instance databases. This chapter also describes the following types of SQL commands in PolarDB-X:

• DDL: You can define, modify, and delete resources in databases by using this language. For example, you can create and delete tables.
• DML: You can change the data content that is stored in databases by using this language. For example, you can add, modify, and delete data.
• Data Query Language (DQL): This language is known as the data retrieval language. You can use this language to retrieve data from tables and specify how to return the data to programs for output.
• Transaction Control Language (TCL): This language ensures the integrity and consistency of databases. The TCL statements in the same transaction all succeed or fail.
• Data Access Language (DAL): You can run commands related to O&M by using this language. You can use these commands to manage and optimize databases.