docs: divide radon_sql_support.md into different files radondb#647

[summary]
divide radon_sql_support.md into different files

[test case]
N/A
[patch codecov]
N/A

docs/radon_sql_statements_manual.md

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+# Reference Manual
+
+On SQL syntax level, RadonDB Fully compatible with MySQL.
+
+In most scenarios, the SQL implementation of RadonDB is a subset of MySQL, for better use and standardization.
+
+RadonDB runs SQL statements in parallel, multiple processes work together simultaneously to run a single SQL statement.
+
+# [Data Definition Statements](sql_statements/Data_Definition_Statements.md)
+# [Data Manipulation Statements](sql_statements/Data_Manipulation_Statements.md)
+# [Database Administration Statements](sql_statements/Database_Administration_Statements.md)
+# [Radon Administration Statements](sql_statements/Radon_Administration_Statements.md)
+# [Others Statements](sql_statements/Others_Statements.md)