T-SQL查询语句(一)：单表查询（国外英文资料）.docVIP

T-SQL查询语句(一)：单表查询（国外英文资料） T-sql query statement (1) : single table lookup T-sql query statement (1) : single table lookup # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # Query statement -- SELECT # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # The query select: 1. Table query 2. Multi-table query 3. Nested query classification 1) single table query 2) multi-table query A. join queries B. the subquery The subquery is a subquery * * * * * * * * * * * * * SQL query statement 1: single table lookup Query all records: select * from table_name The query specifies the field record: the select field list from table_name Filter the same record: the select Distinct field list from table_name The ALL or DISTINCT option in the SELECT statement displays ALL lines that are eligible in the table or deletes the duplicated data row, by default for ALL. With the DISTINCT option, only one row is left in the result set returned by the SELECT for all duplicate data rows. Using distinct will slow down the query speed, and the large number of queries will be more obvious than The query with the expression: select s_name, year (s_birthday) as year from table_name Specify the query results of the query Select top n * from table_name n value is 0-429494967295 Select top n PERCENT * from table_name n value is 0-100 (the previous/post-n rows, before/after n %) Specify query path queries: Select * from database_name.dbo. table_name Form: database name. Database table owner. Table name (you can query the database and the user) Store the query results to another table The select field list into the new table name from the table name Select sno, degree into scorekk from score Select sno, degree into tempdb # is a virtual table that can be created across databases! Change the query shown in the