限制 SQL 查询仅扫描少于 500 条记录的表

Question

我创建了以下脚本，它遍历我数据库所有字段中的所有值。

然而，这是一项非常耗时的任务，因此我希望将其限制为仅遍历包含 500 条或更少记录的 tables，并跳过充满无关紧要的大 tables无论如何数据。

我在弄清楚如何将我的 COUNT 包含在 table 中时遇到问题，因为我正在使用 varchar(256) 作为 table 名称。

USE [Name of Database]
DECLARE @SearchStr nvarchar(100) = 'Text to search fields for'
DECLARE @Results TABLE (ColumnName nvarchar(370), ColumnValue nvarchar(3630))

SET NOCOUNT ON

DECLARE @TableName nvarchar(256), @ColumnName nvarchar(128), @SearchStr2 nvarchar(110)
SET  @TableName = ''
SET @SearchStr2 = QUOTENAME('%' + @SearchStr + '%','''')

WHILE @TableName IS NOT NULL

BEGIN
    SET @ColumnName = ''
    SET @TableName = 
    (
        SELECT MIN(QUOTENAME(TABLE_SCHEMA) + '.' + QUOTENAME(TABLE_NAME))
        FROM     INFORMATION_SCHEMA.TABLES
        WHERE         TABLE_TYPE = 'BASE TABLE'
            AND    QUOTENAME(TABLE_SCHEMA) + '.' + QUOTENAME(TABLE_NAME) > @TableName
            AND    OBJECTPROPERTY(
                    OBJECT_ID(
                        QUOTENAME(TABLE_SCHEMA) + '.' + QUOTENAME(TABLE_NAME)
                         ), 'IsMSShipped'
                           ) = 0
    )

    WHILE (@TableName IS NOT NULL) AND (@ColumnName IS NOT NULL)

    BEGIN
        SET @ColumnName =
        (
            SELECT MIN(QUOTENAME(COLUMN_NAME))
            FROM     INFORMATION_SCHEMA.COLUMNS
            WHERE         TABLE_SCHEMA    = PARSENAME(@TableName, 2)
                AND    TABLE_NAME    = PARSENAME(@TableName, 1)
                AND    DATA_TYPE IN ('char', 'varchar', 'nchar', 'nvarchar', 'int', 'decimal')
                AND    QUOTENAME(COLUMN_NAME) > @ColumnName
        )

        IF @ColumnName IS NOT NULL

        BEGIN
            INSERT INTO @Results
            EXEC
            (
                'SELECT ''' + @TableName + '.' + @ColumnName + ''', LEFT(' + @ColumnName + ', 3630) 
                FROM ' + @TableName + ' (NOLOCK) ' +
                ' WHERE ' + @ColumnName + ' LIKE ' + @SearchStr2
            )
        END
    END    
END

SELECT ColumnName, ColumnValue FROM @Results

如有任何帮助或建议，我们将不胜感激？

Answer 1

您需要做的就是计算 table 的计数并应用

这样的条件

if(select count(*) from table_name)<500
begin
    execute your query
end

Answer 2

您可以使用系统 table sys.dm_db_partition_stats 查找具有 500 多条记录的 table。

/* Returns tables with 500+ rows, 
 * using the system tables.
 */
SELECT
    s.name,
    o.name,
    st.row_count
FROM    
    sys.objects AS o
        INNER JOIN sys.schemas AS s                 ON s.schema_id  = o.schema_id
        INNER JOIN sys.dm_db_partition_stats st     ON st.object_id = o.object_id

WHERE
    o.type = 'U'                -- User defined is a table.     
    AND st.index_id IN (0, 1)   -- 0 = Heap, 1 = Clustered index.
    AND st.row_count > 500
ORDER BY 
    st.row_count DESC
;

返回的行数是一个近似值。除非您需要 100% 的准确性，否则它应该符合您的目的。我针对十亿条记录加数据库测试了查询，发现所有行计数都与基础 tables 完全匹配。有关详细信息，请参阅 docs。

Answer 3

您可以使用 sys.dm_db_partition_stats table 的近似方法。只需按照此代码添加 JOIN 即可：

    ...
    SET @TableName = 
        (
            SELECT MIN(QUOTENAME(TABLE_SCHEMA) + '.' + QUOTENAME(TABLE_NAME))
            FROM     INFORMATION_SCHEMA.TABLES

            --add this JOIN 
            JOIN 
              (
                SELECT
                   object_name(object_id) as Table_Name
                FROM sys.dm_db_partition_stats
                WHERE (index_id < 2)
                GROUP BY object_name(object_id)
                HAVING SUM(row_count)<=500
              ) as Stat
             ON  INFORMATION_SCHEMA.TABLES.TABLE_NAME = Stat.Table_Name
             -- add this JOIN 


             WHERE         TABLE_TYPE = 'BASE TABLE'
                AND    QUOTENAME(TABLE_SCHEMA) + '.' + QUOTENAME(TABLE_NAME) > @TableName
                AND    OBJECTPROPERTY(
                        OBJECT_ID(
                            QUOTENAME(TABLE_SCHEMA) + '.' + QUOTENAME(TABLE_NAME)
                             ), 'IsMSShipped'
                               ) = 0
        )
    ...

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限制 SQL 查询仅扫描少于 500 条记录的表

Limit SQL query to only scan tables with less than 500 records

sql

sql-server

ssms