有时在数据库中创建了一个表格之后,我们发现为该表格加上一个索引有助于该表格的查询速度。要透过SQL 达到这个目的,我们先使用ALTER TABLE指令来告诉数据库我们要更改表格的结构,然后使用ADD INDEX指令告诉数据库我们要添加一个索引。 添加索引的语法为:
ADD [UNIQUE] [INDEX|KEY] index_name USING index_type(column_name[(length)]) [ASC|DESC]; 1. 2. 3. 与CREATE INDEX相比,ALTER TABLE语句在增加索引的同时还可以指定要增加索引的表名。 下面是一个使用ALTER TABLE语句增加B-tree索引的例子: ALTER TABLE table_name ADD INDEX idx_name (column_name)...
In this article, we explore the current options letting us add new columns to an existing table in SQL Server database. The use case may arise on many occasions. Particularly, it happens when there are updates for an application, and they demand adding new columns. Create a Table To begin...
Most of you must have come across the pain of adding a not null column with a default value to an existing big table. It takes minutes to add columns. I recently found out that this problem has been resolved in SQL Server 2012. Let’s look into some ways to resolve this in versions ...
Create the tableCREATETABLEt_account ( AccountKeyintNOTNULL, AccountDescriptionnvarchar(50), AccountTypenvarchar(50), UnitSoldint);--Store the table as a columnstore.CREATECLUSTERED COLUMNSTOREINDEXtaccount_cciONt_account;--Add a nonclustered index.CREATEUNIQUEINDEXtaccount_nc1ONt_account (AccountKey);...
CREATE CLUSTERED COLUMNSTORE INDEX index_name ON [ database_name . [ schema ] . | schema . ] table_name [ORDER (column[,...n])] [WITH ( DROP_EXISTING = { ON | OFF } )] [;] CREATE [ CLUSTERED | NONCLUSTERED ] INDEX index_name ON [ database_name . [ schema ] . | schema...
ALTERTABLEsales_data REPARTITION BY HASH(product_id) PARTITIONS32; 三、高性能执行策略 3.1 批处理与流式处理 java // Java批处理示例(每批5000条) try (PreparedStatement pstmt = conn.prepareStatement(sql)) { for (inti=0;i< batchSize;i++) { ...
Select Filegroup or Partition Scheme Name and select from the list the filegroup or partition scheme to where you want to move the index. Click Close. On the File menu, select Savetable_name. To move an existing index to a different filegroup in Object Explorer In Object Explorer, click the...
(birth), then it is widely used (living), and finally, it is decommissioned (death). A database administrator during this life cycle might be asked to add, change, and drop columns within an existing table. How can we execute these tasks without using the graphical user interface within ...
PARTITION_PREDICATES、DELTA_UNSUPPORTED_TIME_TRAVEL_VIEWS、DELTA_UNSUPPORTED_TYPE_CHANGE_IN_SCHEMA、DELTA_UNSUPPORTED_TYPE_CHANGE_ON_COLUMNS_WITH_BLOOM_FILTER_INDEX、DELTA_UNSUPPORTED_VACUUM_SPECIFIC_PARTITION、DELTA_UNSUPPORTED_WRITES_WITHOUT_COORDINATOR、WRONG_COLUMN_DEFAULTS_FOR_DELTA_ALTER_TABLE_ADD_COLUMN...