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select * from company where comid in (select Max(comid) from company group by companyname)
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select * from company where comid not in (select Max(comid) from company group by companyname)
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SQLÓï¾äPART2

Subquery: (single-row subqueries and multi-rows subqueries).
select select_list
from table
where expr operator (select select_list from table);
single-row subqueries operator: =, >, >=, <, <=, <>
e.g.:
1. select department_id, min(salary) from employees group by department_id ......

SQLÓï¾äPART3

constraint Example:
1. grammer:
 create table [schema.]table
      (column datatype [DEFAULT expr]
     [column_constraint], ...
     [table_constraint] [,......]);
2. example of a column_level constraint:
create table empl ......

SQLÓï¾äPART4

GRANT
Name
GRANT -- ¶¨Òå·ÃÎÊȨÏÞ
Synopsis GRANT { { SELECT | INSERT | UPDATE | DELETE | RULE | REFERENCES | TRIGGER }
    [,...] | ALL [ PRIVILEGES ] }
    ON [ TABLE ] tablename [, ...]
    TO { username | GROUP groupname | PUBLIC } [, ...] [ WI ......

SQLÓï¾äPART7

Merge statement
function benefits: 1) provides the ability to conditionally update, insert or delete data into a database table. 2) performs an update if the row exists, and an insert if it is a new row. --> 1) avoids seperate updates, 2) increase performance and ease of use. 3) is useful in dat ......

SQL ServerÖеÄͨÅä·û

ͨÅä·û_
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if PATINDEX('%[ß¹-×ö]%','ÐèÒªÅжϵÄ×Ö·û')>0 -- ÅжÏÊÇ·ñÓÐ×Ö·û
print 'Óкº×Ö'
else
print 'ÎÞºº×Ö'
ͨÅä·û%
"%"·ûºÅÊÇ×Ö·ûÆ¥Åä·û,ÄÜÆ¥Åä0¸ö»ò¸ü¶à×Ö·ûµÄÈÎÒⳤ¶ ......
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