在执行update命令时,一定不要忘记 where clause, 要不然会update整个table Delete statement delete existing records in a table DELETE FROM table_name WHERE condition; The WHERE clause specifies which record(s) should be deleted. If you omit the WHERE clause, all records in the table will be deleted!
However, they can be referenced by subsequent clauses such as the ORDER BY clause. The query processor determines the actual physical execution of the statement, and the order might vary from this list.FROM ON JOIN WHERE GROUP BY WITH CUBE or WITH ROLLUP HAVING SELECT DISTINCT ORDER BY TOP...
Check if the “current” tuple satisfies the WHERE clause. If so, compute the attributes or expressions of the SELECT clause using the components of this tuple. * In SELECT clauses When there is one relation in the FROM clause, * in the SELECT clause stands for “all attributes of this ...
D. Using the TOP clauseThe following examples use the TOP clause to limit the number of rows that are modified in an UPDATE statement. When a TOP (n) clause is used with UPDATE, the update operation is performed on a random selection of 'n' number of rows. The following example ...
it creates the statistics for the values in all rows. When queries select from a subset of rows, and that subset of rows has a unique data distribution, filtered statistics can improve query plans. You can create filtered statistics by using theCREATE STATISTICSstatement with theWHEREclause to ...
invalid in the HAVING clause because it is not contained in either an aggregate function or the GROUP BY clause question Invalid length parameter passed to the LEFT or SUBSTRING function Invalid object name '##Temp_Data_Final' Invalid object name '#TmpTable' whenselecting from temporary table ma...
DATEDIFF can be used in the select list, WHERE, HAVING, GROUP BY and ORDER BY clauses. In SQL Server 2008, DATEDIFF implicitly casts string literals as datetime2 types. When using DATEDIFF with DATEADD, avoid implicit casts of string literals. For more information, seeDATEADD (Transact-SQL)...
[HAVING clause] [{UNION | UNION ALL} SELECT ...] [ORDER BY clause] [COMPUTE clause] [FOR BROWSE] [OPTION ( query_hints )]Optimizer Hints Oracle-specific, cost-based optimizer hints are not supported by SQL Server. They must be removed from your statement code. The recommended techniqu...
SQL HAVING Use the SQL HAVING clause to filter an aggregated query. Start Now Lesson 8 SQL CASE Using if/then logic with the SQL CASE statement. Start Now Lesson 9 SQL DISTINCT Using SQL DISTINCT to view and aggregate unique values in a given column. ...
SELECT TOPLIMITSELECT TOP PERCENTSELECT TOP and add a WHERE Clause Examples Explained SQL MIN() and MAX() MIN()MAX() Examples Explained SQL COUNT, AVG() and SUM() COUNT()AVG()SUM() Examples Explained SQL LIKE LIKE - select all table rows starting with "a"LIKE - select all table rows...