Query syntax:
SELECT
field list
FROM
list of table names
WHERE
list of conditions
GROUP BY
grouping field
HAVING
Condition after grouping
ORDER BY
sort field
LIMIT
Pagination limited
Query multiple fields:
SELECT field list FROM table name;
SELECT * FROM table name; ——query all data
Remove duplicate records:
SELECT DISTINCT field list FROM table name;
alias:
AS: AS can also be omitted
Conditional query syntax:
SELECT field list FROM table name WHERE condition list;
Sort query syntax:
SELECT field list FROM table name ORDER BY sort field name 1 [sort mode 1], sort field name 2 [sort mode 2]...;
sort by:
ASC: Sort in ascending order (default)
DESC: Sort in descending order
Aggregate function syntax:
SELECT aggregate function name, (column name) FROM table;
Group query syntax:
SELECT field list FROM table name [WHERE condition limit before grouping] GROUP BY group field name [HAVING condition filter after grouping];
Paging query syntax:
SELECT field list FROM table name LIMIT start index, number of query entries;
Inner join query syntax:
Implicit inner join:
SELECT field list FROM table 1, table 2...WHERE condition;
Explicit inner join:
SELECT field list FROM table 1 [INNER] JOIN table 2 ON condition;
Outer join query syntax:
Left outer join:
SELECT field list FROM table 1 LEFT [OUTER] JOIN table 2 ON condition;
Right outer join:
SELECT field list FROM table 1 RIGHT [OUTER] JOIN table 2 ON condition;
subquery:
Single row and single column: as a conditional value, use = != > < etc. for conditional judgment
SELECT field list FROM table WHERE field name = (subquery);
Multi-line single column: as a conditional value, use keywords such as in for conditional judgment
SELECT field list FROM table WHERE field name in (subquery);
Multiple rows and multiple columns: as a virtual table
SELECT field list FROM (subquery) WHERE condition;