这里写自定义目录标题
SELECT *
FROM system.data_type_families
注意：case_insensitive=0 表示大小写敏感。
ClickHouse 的 String 类型、Int 类型、Float 类型、Decimal类型等都是大小写敏感的（case_sensitive=0）。关于ClickHouse大小写敏感，有下面几个注意点。
1.ClickHouse 对于 SQL 语句的解析是大小写敏感的，这意味着 SELECT a 和 SELECT A 表示的语义是不相同的。
2.ClickHouse对关键字大小写不敏感，也就是说SELECT和select都行，不过还是建议遵循规范使用大写。
3.此外，ClickHouse 的一些数据类型也大小写敏感（如表3-1中所示，case_sensitive=0的是大小写敏感的类型），比如：UInt8 不可以写成 uint8，String 不可以写成 string。
4.ClickHouse中大部分的函数也是大小写敏感的。详细的函数清单，可以在ClickHouse Server执行SQL：SELECT * FROM system.functions 查看case_sensitive=0的函数。这些函数都是 ClickHouse 独有的，或者说你在其它关系型数据库中见不到的，比如toDate()函数写成todate()就会报错。但是像 min、max、length、sum、count 等等这些在其它关系型库中也能看到的函数，在 ClickHouse 中则是大小写不敏感的。例如，计算字符串长度的函数length()、Length()都可以返回字符串长度。
5.另外，ClickHouse 中没有 true、false值的布尔类型（Bool），所以，一般用整型（UInt8）表示布尔类型，1 为真，0 为假。
清单表格如下：
name | case_insensitive | alias_to |
JSON | 1 | |
Polygon | 0 | |
Ring | 0 | |
Point | 0 | |
SimpleAggregateFunction | 0 | |
MultiPolygon | 0 | |
IPv6 | 0 | |
UInt32 | 0 | |
IntervalYear | 0 | |
IntervalQuarter | 0 | |
IntervalMonth | 0 | |
Int64 | 0 | |
IntervalDay | 0 | |
IntervalHour | 0 | |
IPv4 | 0 | |
IntervalSecond | 0 | |
LowCardinality | 0 | |
Int16 | 0 | |
UInt256 | 0 | |
AggregateFunction | 0 | |
Nothing | 0 | |
Decimal256 | 1 | |
Tuple | 0 | |
Array | 0 | |
IntervalMicrosecond | 0 | |
Bool | 1 | |
Enum16 | 0 | |
IntervalMinute | 0 | |
FixedString | 0 | |
String | 0 | |
DateTime | 1 | |
Object | 0 | |
Map | 0 | |
UUID | 0 | |
Decimal64 | 1 | |
Nullable | 0 | |
Enum | 1 | |
Int32 | 0 | |
UInt8 | 0 | |
Date | 1 | |
Decimal32 | 1 | |
UInt128 | 0 | |
Float64 | 0 | |
Nested | 0 | |
UInt16 | 0 | |
IntervalMillisecond | 0 | |
Int128 | 0 | |
Decimal128 | 1 | |
Int8 | 0 | |
Decimal | 1 | |
Int256 | 0 | |
DateTime64 | 1 | |
Enum8 | 0 | |
DateTime32 | 1 | |
Date32 | 1 | |
IntervalWeek | 0 | |
UInt64 | 0 | |
IntervalNanosecond | 0 | |
Float32 | 0 | |
bool | 1 | Bool |
INET6 | 1 | IPv6 |
INET4 | 1 | IPv4 |
ENUM | 1 | Enum |
BINARY | 1 | FixedString |
GEOMETRY | 1 | String |
NATIONAL CHAR VARYING | 1 | String |
BINARY VARYING | 1 | String |
NCHAR LARGE OBJECT | 1 | String |
NATIONAL CHARACTER VARYING | 1 | String |
boolean | 1 | Bool |
NATIONAL CHARACTER LARGE OBJECT | 1 | String |
NATIONAL CHARACTER | 1 | String |
NATIONAL CHAR | 1 | String |
CHARACTER VARYING | 1 | String |
LONGBLOB | 1 | String |
TINYBLOB | 1 | String |
MEDIUMTEXT | 1 | String |
TEXT | 1 | String |
VARCHAR2 | 1 | String |
CHARACTER LARGE OBJECT | 1 | String |
DOUBLE PRECISION | 1 | Float64 |
LONGTEXT | 1 | String |
NVARCHAR | 1 | String |
INT1 UNSIGNED | 1 | UInt8 |
VARCHAR | 1 | String |
CHAR VARYING | 1 | String |
MEDIUMBLOB | 1 | String |
NCHAR | 1 | String |
VARBINARY | 1 | String |
CHAR | 1 | String |
SMALLINT UNSIGNED | 1 | UInt16 |
TIMESTAMP | 1 | DateTime |
FIXED | 1 | Decimal |
TINYTEXT | 1 | String |
NUMERIC | 1 | Decimal |
DEC | 1 | Decimal |
TIME | 1 | Int64 |
FLOAT | 1 | Float32 |
SET | 1 | UInt64 |
TINYINT UNSIGNED | 1 | UInt8 |
INTEGER UNSIGNED | 1 | UInt32 |
INT UNSIGNED | 1 | UInt32 |
CLOB | 1 | String |
MEDIUMINT UNSIGNED | 1 | UInt32 |
BLOB | 1 | String |
REAL | 1 | Float32 |
SMALLINT | 1 | Int16 |
INTEGER SIGNED | 1 | Int32 |
NCHAR VARYING | 1 | String |
INT SIGNED | 1 | Int32 |
TINYINT SIGNED | 1 | Int8 |
BIGINT SIGNED | 1 | Int64 |
BINARY LARGE OBJECT | 1 | String |
SMALLINT SIGNED | 1 | Int16 |
YEAR | 1 | UInt16 |
MEDIUMINT | 1 | Int32 |
INTEGER | 1 | Int32 |
INT1 SIGNED | 1 | Int8 |
BIT | 1 | UInt64 |
BIGINT UNSIGNED | 1 | UInt64 |
BYTEA | 1 | String |
INT | 1 | Int32 |
SINGLE | 1 | Float32 |
MEDIUMINT SIGNED | 1 | Int32 |
DOUBLE | 1 | Float64 |
INT1 | 1 | Int8 |
CHAR LARGE OBJECT | 1 | String |
TINYINT | 1 | Int8 |
BIGINT | 1 | Int64 |
CHARACTER | 1 | String |
BYTE | 1 | Int8 |
