Ms sql server tips 1 0
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This document provides an overview of MS SQL Server tips covering topics such as relationship databases, database design including normalization, indexes, and useful queries. Relationship databases organize information into tables that can be related through primary and foreign keys. Database design involves normalization to eliminate anomalies and improve performance. Indexes help optimize queries and common types include clustered, nonclustered, unique and full-text. Useful queries are provided to check index fragmentation and monitor currently running processes.
![RELATIONSHIP DATABASE MANAGEMENT SYSTEM
Primary Key :
Primary key fields must be unique and cannot contain a null value
Each table should have a primary key field[s].
Composite Key: Using more than one field as a primary key.
Foreign Key :
Fields in a table that refer to the primary key in another table.
The data in this field must exactly match data contained in the primary key](https://image.slidesharecdn.com/mssqlservertips10-181024081228/85/Ms-sql-server-tips-1-0-4-320.jpg)
Ms sql server tips 1 0
- 1. MS SQL SERVER TIPS By Arman Aug-18
- 2. • Relationship Database Management System • Database Design • Indexes • Useful Queries
- 3. RELATIONSHIP DATABASE MANAGEMENT SYSTEM Collection of information organized in tables Tables are also “Relations” Tables are constructed and associated to each other through shared fields. Fields are also “Columns” or “Attributes” A set of attributes comprises a record Records are also “Rows” or “Tuples” Tables are related through common fields designated as primary key and foreign keys. Allow us to find, update, and delete data quickly, and help to ensure accuracy
- 4. RELATIONSHIP DATABASE MANAGEMENT SYSTEM Primary Key : Primary key fields must be unique and cannot contain a null value Each table should have a primary key field[s]. Composite Key: Using more than one field as a primary key. Foreign Key : Fields in a table that refer to the primary key in another table. The data in this field must exactly match data contained in the primary key
- 5. DATABASE DESIGN RELATIONSHIP TYPES One-to-one relationships One-to-many relationships Many-to-many relationships Mandatory or not?
- 6. DATABASE DESIGN NORMALIZATION First normal form (1NF) Second normal form (2NF) Third normal form (3NF)
- 7. DATABASE DESIGN NORMALIZATION 1NF First normal form (1NF) I. It should only have single(atomic) valued attributes/columns. II. Values stored in a column should be of the same domain III. All the columns in a table should have unique names. IV. And the order in which data is stored, does not matter.
- 8. DATABASE DESIGN NORMALIZATION 2NF Second normal form (2NF) I. It should be in the First Normal form. II. And, it should not have Partial Dependency.
- 9. DATABASE DESIGN NORMALIZATION 3NF Third normal form (3NF) I. It is in the Second Normal form. II. And, it doesn't have Transitive Dependency.
- 10. DATABASE DESIGN NORMALIZATION BCNF Boyce-Codd Normal Form (BCNF) I. It should be in the Third Normal Form. II. And, for any dependency A → B, A should be a super key.
- 11. DATABASE DESIGN NORMALIZATION 4NF Fourth Normal Form (4NF)
- 12. INDEXES TYPES Regulations 1 Clustered Index per Table 249 Non Clustered (2005) 999 Non Clustered (2008+) 16 Columns or 900 Bytes Clustered Index Nonclustered Index Unique index Filtered index Full-Text XML
- 13. CLUSTERED TABLE VS HEAP TABLE Clustered Indexed Table Heap Table
- 14. CLUSTERED INDEX Clustered Index – sort order of the data within the table on the hard drive and in memory. One per table Desired Qualities Narrow Data Type Unique Static Increasing
- 15. NONCLUSTERED INDEX Cover Common Queries Link to Clustered Indexes through Key Bookmark (Key/RID) Lookup
- 16. FRAGMENTATION Identifying Fragmentation 2005 DBCC SHOWCONTIG Above 2005 sys.dm_db_index_physical_stats Required Actions avg_fragmentation_in_percent value Corrective statement > 5% and < = 30% ALTER INDEX REORGANIZE > 30% ALTER INDEX REBUILD WITH (ONLINE = ON)
- 17. USEFUL QUERIES Check index fragmentation using Transact-SQL 2012 2005 DBCC SHOWCONTIG WITH TABLERESULTS, ALL_INDEXES; Currently running process SELECT sqltext.TEXT, req.session_id, req.status,req.command, req.cpu_time, req.total_elapsed_time ,blocking_session_id ,wait_time ,wait_type ,logical_reads FROM sys.dm_exec_requests req CROSS APPLY sys.dm_exec_sql_text(sql_handle) AS sqltext SELECT a.index_id, name, avg_fragmentation_in_percent FROM sys.dm_db_index_physical_stats (DB_ID(N'UniversoDB2018'), OBJECT_ID(N'dbo.tblindividual'), NULL, NULL, NULL) AS a JOIN sys.indexes AS b ON a.object_id = b.object_id AND a.index_id = b.index_id;
- 18. USEFUL QUERIES Check index fragmentation using Transact-SQL SELECT TOP 10 SUBSTRING(qt.TEXT, (qs.statement_start_offset/2)+1, ((CASE qs.statement_end_offset WHEN -1 THEN DATALENGTH(qt.TEXT) ELSE qs.statement_end_offset END - qs.statement_start_offset)/2)+1), qs.execution_count, qs.total_logical_reads, qs.last_logical_reads, qs.total_logical_writes, qs.last_logical_writes, qs.total_worker_time, qs.last_worker_time, qs.total_elapsed_time/1000000 total_elapsed_time_in_S, qs.last_elapsed_time/1000000 last_elapsed_time_in_S, qs.last_execution_time, qp.query_plan FROM sys.dm_exec_query_stats qs CROSS APPLY sys.dm_exec_sql_text(qs.sql_handle) qt CROSS APPLY sys.dm_exec_query_plan(qs.plan_handle) qp ORDER BY qs.total_logical_reads DESC -- logical reads -- ORDER BY qs.total_logical_writes DESC -- logical writes -- ORDER BY qs.total_worker_time DESC -- CPU time
- 19. READ TYPES Index Scan Table Scan (Heap) Index Seek Key Lookup RID Lookup (heap)
- 20. RULES FOR EXECUTION PLAN COMPILATION Build up most resource efficient plan AS little page reads as possible Fastest Operation possible Choosing Indexes: Prefer read range over scan Prefer small indexes over large
Editor's Notes
- #7: Student and Branch Example Insertion Anomaly Updation Anomaly Deletion Anomaly
- #8: Student and Branch Example Insertion Anomaly Updation Anomaly Deletion Anomaly
- #9: Student and Branch Example Insertion Anomaly Updation Anomaly Deletion Anomaly
- #10: Student and Branch Example Insertion Anomaly Updation Anomaly Deletion Anomaly
- #11: In the table above, student_id, subject form primary key, which means subject column is a prime attribute. But, there is one more dependency, professor → subject. And while subject is a prime attribute, professor is a non-prime attribute, which is not allowed by BCNF.
- #12: For a dependency A → B, if for a single value of A, multiple value of B exists, then the table may have multi-valued dependency. Also, a table should have at-least 3 columns for it to have a multi-valued dependency. And, for a relation R(A,B,C), if there is a multi-valued dependency between, A and B, then B and C should be independent of each other.
- #14: HEAP Data is not stored in any particular order Specific data can not be retrieved quickly, unless there are also non-clustered indexes Data pages are not linked, so sequential access needs to refer back to the index allocation map (IAM) pages Since there is no clustered index, additional time is not needed to maintain the index Since there is no clustered index, there is not the need for additional space to store the clustered index tree These tables have a index_id value of 0 in the sys.indexes catalog view Clustered Indexed Table Data is stored in order based on the clustered index key Data can be retrieved quickly based on the clustered index key, if the query uses the indexed columns Data pages are linked for faster sequential access Additional time is needed to maintain clustered index based on INSERTS, UPDATES and DELETES Additional space is needed to store clustered index tree These tables have a index_id value of 1 in the sys.indexes catalog view
- #15: Clustered Clustered indexes sort and store the data rows in the table or view based on their key values. These are the columns included in the index definition. There can be only one clustered index per table, because the data rows themselves can be stored in only one order. The only time the data rows in a table are stored in sorted order is when the table contains a clustered index. When a table has a clustered index, the table is called a clustered table. If a table has no clustered index, its data rows are stored in an unordered structure called a heap.
- #16: Nonclustered Nonclustered indexes have a structure separate from the data rows. A nonclustered index contains the nonclustered index key values and each key value entry has a pointer to the data row that contains the key value. The pointer from an index row in a nonclustered index to a data row is called a row locator. The structure of the row locator depends on whether the data pages are stored in a heap or a clustered table. For a heap, a row locator is a pointer to the row. For a clustered table, the row locator is the clustered index key. You can add nonkey columns to the leaf level of the nonclustered index to by-pass existing index key limits, and execute fully covered, indexed, queries.